95ZJ_14.PDF

FUEL SYSTEM

CONTENTS

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ACCELERATOR PEDAL AND THROTTLE CABLE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

FUEL DELIVERY SYSTEM . . . . . . . . . . . . . . . . . . 3FUEL TANKS . . . . . . . . . . . . . . . . . . . . . . . . . . . 12GENERAL INFORMATION . . . . . . . . . . . . . . . . . . 1MULTI-PORT FUEL INJECTION (MFI)—4.0L 6

CYL. ENGINE—COMPONENT DESCRIPTION/SYSTEM OPERATION . . . . . . . . . . . . . . . . . . . 17

MULTI-PORT FUEL INJECTION (MFI)—4.0L 6CYL. ENGINE—COMPONENT REMOVAL/INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 45

MULTI-PORT FUEL INJECTION (MFI)—4.0L 6CYL. ENGINE—GENERAL DIAGNOSIS . . . . . 29

MULTI-PORT FUEL INJECTION (MFI)—5.2L V-8ENGINE—COMPONENT DESCRIPTION/SYSTEM OPERATION . . . . . . . . . . . . . . . . . . . 53

MULTI-PORT FUEL INJECTION (MFI)—5.2L V-8ENGINE—COMPONENT REMOVAL/INSTALLATION . . . . . . . . . . . . . . . . . . . . . . . . 85

MULTI-PORT FUEL INJECTION (MFI)—5.2L V-8ENGINE—GENERAL DIAGNOSIS . . . . . . . . . . 66

SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . 95

GENERAL INFORMATION

Throughout this group, references are made to par-ticular vehicle models by alphabetical designation orby the particular vehicle nameplate. A chart showinga breakdown of the alphabetical designations is in-cluded in the Introduction section at the beginning ofthis manual.

The Fuel System consists of: the fuel tank, anelectric (fuel tank mounted) fuel pump, a fuel pres-sure regulator, fuel filter, sensors, switches and pow-ertrain control module (PCM). It also consists of fueltubes/lines/hoses, vacuum hoses, throttle body, fuelrail and fuel injectors.

The Fuel Delivery System consists of: the electricfuel pump, a frame mounted fuel filter, fuel tubes/lines/hoses, fuel rail, fuel injectors and fuel pressureregulator.

A Fuel Return System is used on all models witheither a 4.0L or 5.2L engine. A separate fuel returnline from the engine to the tank is no longer used onany 4.0L or 5.2L engine. Excess fuel is returnedthrough the fuel pump module and back into the fueltank through the fuel pressure regulator. The fuelpressure regulator is located in the fuel tank withinthe fuel pump module.

The Fuel Tank Assembly consists of: the fueltank, filler tube, fuel gauge sending unit/electric fuelpump module, a fuel pressure regulator mounted tothe fuel pump module, a pressure relief/rollover valveand a pressure-vacuum filler cap.

Also to be considered part of the fuel system is theEvaporation Control System. This is designed toreduce the emission of fuel vapors into the atmo-sphere. The description and function of the Evapora-

tive Control System is found in Group 25, EmissionControl Systems.

FUEL USAGE STATEMENTYour vehicle was designed to meet all emission reg-

ulations and provide excellent fuel economy usinghigh quality unleaded gasoline. Only use unleadedgasolines having a minimum posted octane of 87.

If your vehicle develops occasional light sparkknock (ping) at low engine speeds, this is not harm-ful. However, continued heavy knock at highspeeds can cause damage and should be re-ported to your dealer immediately. Engine dam-age as a result of heavy knock operation may not becovered by the new vehicle warranty.

In addition to using unleaded gasoline with theproper octane rating, those that contain deter-gents, corrosion and stability additives are rec-ommended. Using gasolines that have theseadditives will help improve fuel economy, reduceemissions and maintain vehicle performance.

Poor quality gasoline can cause problems suchas hard starting, stalling and stumble. If you experi-ence these problems, use another brand of gasolinebefore considering service for the vehicle.

GASOLINE/OXYGENATE BLENDSSome fuel suppliers blend unleaded gasoline with

materials that contain oxygen such as alcohol, MTBEand ETBE. The type and amount of oxygenate usedin the blend is important. The following are generallyused in gasoline blends:

ZJ FUEL SYSTEM 14 - 1

ETHANOLEthanol (Ethyl or Grain Alcohol) properly blended,

is used as a mixture of 10 percent ethanol and 90percent gasoline. Gasoline with ethanol may beused in your vehicle.

METHANOL

CAUTION: DO NOT USE GASOLINES CONTAININGMETHANOL. Use of methanol/gasoline blends may re-sult in starting and driveability problems. In addition,damage may be done to critical fuel system compo-nents.

Methanol (Methyl or Wood Alcohol) is used in a va-riety of concentrations blended with unleaded gaso-line. You may encounter fuels containing 3 percent ormore methanol along with other alcohols called cosol-vents.

Problems that are the result of using methanol/gas-oline blends are not the responsibility of ChryslerCorporation. They may not be covered by the vehiclewarranty.

MTBE/ETBEGasoline and MTBE (Methyl Tertiary Butyl Ether)

blends are a mixture of unleaded gasoline and up to15 percent MTBE. Gasoline and ETBE (Ethyl Ter-tiary Butyl Ether) are blends of gasoline and up to17 percent ETBE. Gasoline blended with MTBE orETBE may be used in your vehicle.

CLEAN AIR GASOLINEMany gasolines are now being blended that con-

tribute to cleaner air, especially in those areas of thecountry where air pollution levels are high. Thesenew blends provide a cleaner burning fuel and someare referred to as Reformulated Gasoline.

In areas of the country where carbon monoxide lev-els are high, gasolines are being treated with oxygen-ated materials such as MTBE, ETBE and ethanol.

Chrysler Corporation supports these efforts towardcleaner air and recommends that you use these gaso-lines as they become available.

14 - 2 FUEL SYSTEM ZJ

FUEL DELIVERY SYSTEM

INDEX

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Fuel Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Fuel Line with Latch Clip . . . . . . . . . . . . . . . . . . . . 10Fuel Pressure Leak Down Test . . . . . . . . . . . . . . . . 6Fuel Pressure Regulator . . . . . . . . . . . . . . . . . . . . . 4Fuel Pump Capacity Test . . . . . . . . . . . . . . . . . . . . 5Fuel Pump Electrical Control . . . . . . . . . . . . . . . . . . 4

Fuel Pump Module . . . . . . . . . . . . . . . . . . . . . . . . . 3Fuel System Pressure Release Procedure . . . . . . . . 4Fuel System Pressure Test . . . . . . . . . . . . . . . . . . . 5Fuel Tubes/Lines/Hoses and Clamps . . . . . . . . . . . . 7Quick-Connect Fittings . . . . . . . . . . . . . . . . . . . . . . 7

FUEL PUMP MODULEThe fuel pump module is installed in the top of the

fuel tank (Fig. 1). The fuel pressure regulator is apart of the fuel pump module assembly and is nolonger mounted to the fuel rail on either engine. Thefuel pump module contains the following components:• Electric fuel pump• Fuel pressure regulator• Fuel pump reservoir• In-tank fuel filter• Fuel gauge sending unit• Fuel supply line (tube) connection

The fuel pump used on all models is driven by apermanent magnet 12 volt electric motor that is im-mersed in the fuel tank. The electrical pump is inte-gral with the fuel sender unit. The pump/senderassembly is installed inside the fuel tank.

The fuel pump has a check valve at the outlet endthat consists of a ball held against a seat by force ap-plied from a spring. When the pump is operating,fuel pressure overcomes spring pressure and forcesthe ball off its seat, allowing fuel to flow. When thepump is not operating, spring pressure forces the ballback against the seat preventing fuel backflowthrough the pump.

The fuel pump module is not serviceable. If theelectric fuel pump or the fuel pressure regulatorneeds replacement, the complete fuel pump modulemust be replaced.

REMOVAL

WARNING: THE FUEL SYSTEM IS UNDER A CON-STANT PRESSURE EVEN WITH THE ENGINE OFF.BEFORE SERVICING THE FUEL PUMP MODULE,THE FUEL SYSTEM PRESSURE MUST BE RE-LEASED. REFER TO THE FUEL SYSTEM PRES-SURE RELEASE PROCEDURE IN THIS GROUP.

(1) Drain and remove the fuel tank. Refer to FuelTank removal and installation in the Fuel Tank sec-tion of this group.

(2) The fuel pump module locknut is threaded ontothe fuel tank. Remove the fuel pump module locknut(Fig. 2). The fuel pump module will spring up fromthe fuel tank after the locknut has been removed.

(3) Remove module from fuel tank.

INSTALLATION

CAUTION: Whenever the fuel pump module is ser-viced, the rubber gasket must be replaced.

Fig. 1 Fuel Pump Module Location

Fig. 2 Top View of Fuel Pump Module—Typical

ZJ FUEL DELIVERY SYSTEM 14 - 3

(1) Clean the fuel tank at the module opening.(2) Using a new gasket on the fuel tank (Fig. 3),

position fuel pump module into opening in fuel tank.Refer to figure 2 for rotational position.

(3) Tighten locknut.(4) Install fuel tank. Refer to Fuel Tank Installa-

tion in this group.

FUEL PUMP REPLACEMENTThe electric fuel pump is not serviceable. If the fuel

pump needs replacement, the complete fuel pumpmodule must be replaced. Refer to the previous pro-cedure.

FUEL GAUGE SENDING UNIT REPLACEMENTThe fuel gauge sending unit is not serviceable. If

the unit needs replacement, the complete fuel pumpmodule must be replaced.

FUEL PRESSURE REGULATOR

ALL ENGINESA fuel pressure regulator is used with all engines.

It is mounted inside of the fuel pump module (Fig. 4)and is suspended in fuel.

The vacuum assisted fuel pressure regulatorlocated on the fuel rail is no longer used on the4.0L or 5.2L engine.

Fuel Pressure Regulator Operation: The pres-sure regulator is a mechanical device that is not con-trolled by engine vacuum or by the powertraincontrol module (PCM).

The regulator is calibrated to maintain a constantpressure at the fuel pump module outlet fitting of269-283 kPa (39-41 psi). System operating pressureat the fuel injectors, as measured at the fuel rail testport is 255-283 kPa (39 psi 6 2 psi). The regulatorcontains a diaphragm, calibrated springs and a fuelreturn valve.

Fuel is supplied to the regulator by the electric fuelpump. The fuel pump also contains a check valve tomaintain some fuel pressure at the fuel injectorswhen the engine is not operating. This will help tostart the engine.

If fuel pressure at the pressure regulator exceeds269-283 kPa (39-41 psi), an internal diaphragmcloses and excess fuel pressure is routed back intothe fuel tank through the pressure regulator. A sep-arate fuel return line to the engine is no longer usedwith any 4.0L or 5.2L engine.

REMOVAL/INSTALLATIONThe fuel pressure regulator is not serviced sepa-

rately. If the pressure regulator needs replacement,the fuel pump module must be replaced. Refer toFuel Pump Module Removal/Installation for proce-dures.

FUEL PUMP ELECTRICAL CONTROLThe powertrain control module (PCM) computer en-

ergizes the fuel pump through the fuel pump relay.Battery voltage is applied to the relay from the igni-tion switch. The coil in the relay is energized when aground is provided by the PCM. The relay is locatedin the power distribution center (PDC) next to thebattery (Fig. 5). For location of relay within the PDC,refer to label under PDC cover.

Also refer to either of the MFI System—ComponentDescription/System Operation sections of this group.See Automatic Shutdown (ASD) Relay—PCM Output.

FUEL SYSTEM PRESSURE RELEASE PROCEDURE

WARNING: THE FUEL SYSTEM IS UNDER CON-STANT FUEL PRESSURE EVEN WITH THE ENGINEOFF. THIS PRESSURE MUST BE RELEASED BE-FORE SERVICING ANY FUEL SUPPLY SYSTEMCOMPONENT.

(1) Disconnect negative battery cable.

Fig. 3 Rubber Gasket

Fig. 4 Fuel Pressure Regulator Location

14 - 4 FUEL DELIVERY SYSTEM ZJ

(2) Remove fuel tank filler neck cap to release fueltank pressure.

WARNING: DO NOT ALLOW FUEL TO SPILL ONTOTHE ENGINE INTAKE OR EXHAUST MANIFOLDS.PLACE SHOP TOWELS UNDER AND AROUND THEPRESSURE PORT TO ABSORB FUEL WHEN THEPRESSURE IS RELEASED FROM THE FUEL RAIL.

WARNING: WEAR PROPER EYE PROTECTIONWHEN RELEASING FUEL SYSTEM PRESSURE.

(3) Remove protective cap from pressure test porton the fuel rail (Figs. 6 or 7).

(4) Obtain the fuel pressure gauge/hose assemblyfrom fuel pressure gauge tool set 5069. Remove thegauge from the hose.

(5) Place one end of hose (gauge end) into an ap-proved gasoline container.

(6) Place a shop towel under the test port.(7) To release fuel pressure, screw the other end of

hose onto the fuel pressure test port.(8) After fuel pressure has been released, remove

the hose from the test port.(9) Install protective cap to fuel test port.

FUEL SYSTEM PRESSURE TESTThe vacuum assisted fuel pressure regulator

located on the fuel rail is no longer used on the4.0L or 5.2L engine.

Fuel systems on the 4.0L and 5.2L engines areequipped with a fuel tank module mounted, fuelpressure regulator (Fig. 4). The fuel pressure regula-tor is a mechanical device that is not controlled bythe powertrain control module (PCM) or by enginevacuum.

With engine at idle speed, system fuel pressureshould be 255-283 kPa (39 psi 6 2 psi).

(1) Remove the protective cap at the fuel rail (Figs.6 or 7). Connect the 0-414 kPa (0-60 psi) fuel pres-sure gauge (from Gauge Set 5069) to test port pres-sure fitting on fuel rail (Fig. 8).

(2) Note pressure gauge reading. Fuel pressureshould be 255-283 kPa (39 psi 6 2 psi) at idle.

(3) If pressure is at O psi, connect DRB scan tooland refer to operating instructions in the appropriatePowertrain Diagnostics Procedures service manual.

If operating pressure is above 41 psi, the electricfuel pump is OK, but the fuel pressure regulator ifdefective. Replace fuel pump module assembly.

FUEL PUMP CAPACITY TESTBefore performing this test, verify fuel pump pres-

sure by performing the previous tests.

Fig. 5 Power Distribution Center

Fig. 6 Pressure Test Port Location—4.0L Engine

Fig. 7 Pressure Test Port Location—5.2L Engine


(1) Release the fuel system pressure from fuel sys-tem. Refer to the previous Fuel System Pressure Re-lease Procedure in this group.

(2) Disconnect the fuel supply line at the fuel rail.Refer to Fuel Tubes/Lines/Hoses and Clamps in thissection of the group for procedures.

(3) Connect Fuel Line Pressure Test Adapter Toolnumber 6631 (3/8 in.) into the disconnected fuel sup-ply line. Insert the other end of tool 6631 into an ap-proved gasoline container.

(4) To activate the fuel pump and pressurize thesystem, obtain the DRB scan tool. Refer to the appro-priate Powertrain Diagnostic Procedures servicemanual for DRB operation.

(5) A good fuel pump will deliver at least 1 liter offuel per minute.

FUEL PRESSURE LEAK DOWN TEST

ENGINE OFFAbnormally long periods of cranking to restart a

hot engine that has been shut down for a short pe-riod of time may be caused by:• Fuel pressure bleeding past a fuel injector(s).• Fuel pressure bleeding past the check valve in thefuel pump module.

(1) Disconnect the fuel inlet line at fuel rail. Referto Fuel Tubes/Lines/Hoses and Clamps in this sectionof the group for procedures.

(2) Connect Fuel Line Pressure Test Adapter Toolnumber 6539 (5/16 in.), or Adapter Tool number 6631(3/8 in.) between the disconnected fuel line and fuelrail (Fig. 9).

(3) Connect the 0-414 kPa (0-60 psi) fuel pressuretest gauge (from Gauge Set 5069) to the test port oneither tool 6631 or 6539. The fittings on both toolsmust be in good condition and free from anysmall leaks before performing the proceedingtest.

(4) Start engine and bring to normal operatingtemperature.

(5) Observe test gauge. Normal operating pressureat the fuel rail test port should be 255-283 kPa (39psi 6 2 psi).

(6) Shut engine off.(7) Pressure should not fall below 24 psi for five

minutes.(8) If pressure falls below 24 psi, it must deter-

mined if a fuel injector, the fuel module mounted fuelpressure regulator or a fuel tube/line is leaking.

(9) Again, start engine and bring to normal operat-ing temperature.

(10) Shut engine off.(11) Checking for fuel injector leakage: Clamp

off the rubber hose portion of either tool 6539 or 6631between the disconnected fuel tube (line) and testport inlet. If pressure now holds at or above 24 psi, afuel injector or the fuel rail is leaking.

Checking for fuel pump module or fuel tubeleakage: Clamp off the rubber hose portion of eithertool 6539 or 6631 between the fuel rail and test portinlet. If pressure now holds at or above 24 psi, a leakcan be found at a fuel tube/line. If no leaks are foundat fuel tubes or lines, replace the fuel pump module.

MECHANICAL MALFUNCTIONSMechanical malfunctions are more difficult to diag-

nose with this system. The powertrain control mod-ule (PCM) has been programmed to compensate forsome mechanical malfunctions such as incorrect camtiming, vacuum leaks, etc. If engine performanceproblems are encountered and diagnostic trouble

Fig. 8 Typical Fuel Pressure Test Connection

Fig. 9 Connecting Adapter Tool—Typical


codes are not displayed, the problem may be mechan-ical rather than electronic.

FUEL FILTERThe fuel filter protects the fuel injectors from dirt,

water and other foreign matter. The filter is locatedunder the vehicle near the front of fuel tank (Fig.10). Replace fuel filter at intervals specified in theLubrication and Maintenance Schedule chart foundin Group 0, Lubrication and Maintenance.

REMOVAL

WARNING: THE FUEL SYSTEM IS UNDER CON-STANT FUEL PRESSURE EVEN WITH THE ENGINEOFF. THIS PRESSURE MUST BE RELEASED BE-FORE SERVICING THE FUEL FILTER.

(1) Disconnect negative battery cable. Remove fuelfiller cap.

(2) Release fuel system pressure. Refer to the pre-vious Fuel System Pressure Release Procedure inthis section.

(3) Raise and support vehicle.(4) Place shop towels under fuel filter.(5) Disconnect fuel lines at filter. Refer to Quick-

Connect Fittings in this group for procedures.

(6) Remove retaining strap mounting bolt (Fig. 10).(7) Remove filter retaining strap (Fig. 10).(8) Remove filter from mounting bracket.

INSTALLATION

CAUTION: The ends of the fuel filter are marked forcorrect installation. Install filter with the end markedIN towards fuel tank and the end marked OUT to-wards engine.

(1) Place fuel filter in retaining strap with themarked ends in the correct position.

(2) Install retaining strap bolt. Tighten to 7 Nzm(66 in. lbs.) torque.

(3) Install fuel lines to filter. Refer to Fuel Tubes/Lines/Hoses and Clamps in this group. Also refer toQuick-Connect Fittings in this group for procedures.

(4) Lower vehicle.(5) Connect negative battery cable.(6) Start engine and check for leaks.

FUEL TUBES/LINES/HOSES AND CLAMPSAlso refer to the proceeding section on Quick-Con-

nect Fittings.

WARNING: THE FUEL SYSTEM IS UNDER A CON-STANT PRESSURE EVEN WITH THE ENGINE OFF.BEFORE SERVICING ANY FUEL SYSTEM HOSES,FITTINGS OR LINES, THE FUEL SYSTEM PRES-SURE MUST BE RELEASED. REFER TO THE FUELSYSTEM PRESSURE RELEASE PROCEDURE INTHIS GROUP.

Inspect all hose connections such as clamps, cou-plings and fittings to make sure they are secure andleaks are not present. The component should be re-placed immediately if there is any evidence of degra-dation that could result in failure.

Never attempt to repair a plastic fuel line/tube. Re-place as necessary.

Avoid contact of any fuel tubes/hoses with other ve-hicle components that could cause abrasions or scuff-ing. Be sure that the plastic fuel lines/tubes areproperly routed to prevent pinching and to avoid heatsources.

The lines/tubes/hoses used on fuel injected vehiclesare of a special construction. This is due to thehigher fuel pressures and the possibility of contami-nated fuel in this system. If it is necessary to replacethese lines/tubes/hoses, only those marked EFM/EFImay be used.

The hose clamps used to secure rubber hoses onfuel injected vehicles are of a special rolled edge con-struction. This construction is used to prevent theedge of the clamp from cutting into the hose. Onlythese rolled edge type clamps may be used in thissystem. All other types of clamps may cut into thehoses and cause high-pressure fuel leaks.

Use new original equipment type hose clamps.Tighten hose clamps to 1 Nzm (15 in. lbs.) torque.

QUICK-CONNECT FITTINGSAlso refer to the previous Fuel Tubes/Lines/Hoses

and Clamps section.Different types of quick-connect fittings are used to

attach various fuel system components. These are: asingle-tab type, a two-tab type or a plastic retainerring type.

Fig. 10 Fuel Filter


SINGLE-TAB TYPEThis type of fitting is equipped with a single pull

tab (Fig. 11). The tab is removable. After the tab isremoved, the quick-connect fitting can be separatedfrom the fuel system component.

CAUTION: The interior components (o-rings, spac-ers) of this type of quick-connect fitting are not ser-viced separately, but new pull tabs are available. Donot attempt to repair damaged fittings or fuel lines/tubes. If repair is necessary, replace the completefuel tube assembly.


DISCONNECTION/CONNECTION(1) Disconnect negative battery cable from battery.(2) Perform the fuel pressure release procedure.

Refer to the Fuel System Pressure Release Procedurein this section.

(3) Clean the fitting of any foreign material beforedisassembly.

(4) Press the release tab on the side of fitting to re-lease pull tab (Fig. 11).

CAUTION: If this release tab is not pressed prior toreleasing the pull tab, the pull tab will be damaged.

(5) While pressing the release tab on the side ofthe fitting, use a screwdriver to pry up the pull tab(Fig. 12).

(6) Raise the pull tab until it separates from thequick-connect fitting (Fig. 13). Discard the old pulltab.

(7) Disconnect the quick-connect fitting from thefuel system component being serviced.

(8) Inspect the quick-connect fitting body and fuelsystem component for damage. Replace as necessary.

(9) Prior to connecting the quick-connect fitting tocomponent being serviced, check condition of fittingand component. Clean the parts with a lint-freecloth. Lubricate them with clean engine oil.

(10) Insert the quick-connect fitting into the fueltube or fuel system component until the built-on stopon the fuel tube or component rests against back offitting.

(11) Obtain a new pull tab. Push the new tab downuntil it locks into place in the quick-connect fitting.

(12) Verify a locked condition by firmly pulling onfuel tube and fitting.

(13) Connect negative cable to battery.(14) Start engine and check for leaks.

Fig. 11 Single-Tab Type Fitting

Fig. 12 Disconnecting Single-Tab Type Fitting

Fig. 13 Removing Pull Tab


TWO-TAB TYPE FITTINGThis type of fitting is equipped with tabs located on

both sides of the fitting (Fig. 14). These tabs are sup-plied for disconnecting the quick-connect fitting fromcomponent being serviced.

CAUTION: The interior components (o-rings, spac-ers) of this type of quick-connect fitting are not ser-viced separately, but new plastic retainers areavailable. Do not attempt to repair damaged fittingsor fuel lines/tubes. If repair is necessary, replacethe complete fuel tube assembly.


DISCONNECTION/CONNECTION(1) Disconnect negative battery cable from the bat-

tery.(2) Perform the fuel pressure release procedure.



(4) To disconnect the quick-connect fitting, squeezethe plastic retainer tabs against the sides of thequick-connect fitting with your fingers. Tool use isnot required for removal and may damage plastic re-tainer. Pull the fitting from the fuel system compo-nent being serviced. The plastic retainer will remainon the component being serviced after fitting is dis-connected. The o-rings and spacer will remain in thequick-connect fitting connector body.

(5) Inspect the quick-connect fitting body and com-ponent for damage. Replace as necessary.

CAUTION: When the quick-connect fitting was dis-connected, the plastic retainer will remain on thecomponent being serviced. If this retainer must beremoved, very carefully release the retainer fromthe component with two small screwdrivers. Afterremoval, inspect the retainer for cracks or any dam-age.


(7) Insert the quick-connect fitting to the compo-nent being serviced and into the plastic retainer.When a connection is made, a click will be heard.


(9) Connect negative cable to battery.(10) Start engine and check for leaks.

PLASTIC RETAINER RING TYPE FITTINGThis type of fitting can be identified by the use of a

full-round plastic retainer ring (Fig. 15) usually blackin color.

CAUTION: The interior components (o-rings, spac-ers, retainers) of this type of quick-connect fittingare not serviced separately. Do not attempt to repairdamaged fittings or fuel lines/tubes. If repair is nec-essary, replace the complete fuel tube assembly.

Fig. 14 Typical Two-Tab Type Quick-Connect Fitting

Fig. 15 Plastic Retainer Ring Type Fitting



DISCONNECTION/CONNECTION(1) Disconnect negative battery cable from the bat-

tery.(2) Perform the fuel pressure release procedure.



(4) To release the fuel system component from thequick-connect fitting, firmly push the fitting towardsthe component being serviced while firmly pushingthe plastic retainer ring into the fitting (Fig. 15).With the plastic ring depressed, pull the fitting fromthe component. The plastic retainer ring must bepressed squarely into the fitting body. If this re-tainer is cocked during removal, it may be dif-ficult to disconnect fitting. Use an open-endwrench on the shoulder of the plastic retainerring to aid in disconnection.

After disconnection, the plastic retainer ring willremain with the quick-connect fitting connector body.

(5) Inspect fitting connector body, plastic retainerring and fuel system component for damage. Replaceas necessary.


(7) Insert the quick-connect fitting into the compo-nent being serviced until a click is felt.


(9) Connect negative battery cable to battery.(10) Start engine and check for leaks.

FUEL LINE WITH LATCH CLIP

DISCONNECTION/CONNECTION AT FUEL RAILA latch clip is used to secure the fuel line to the

fuel rail on the 5.2L V-8 engine (Fig. 16). A specialtool will be necessary to separate the fuel line fromthe fuel rail after the latch clip is removed.

(1) Disconnect the negative battery cable from bat-tery.

(2) Perform the fuel pressure release procedure.Refer to the Fuel System Pressure Release Procedurein this section.


(4) Pry up on the latch clip with a screwdriver(Fig. 17).

(5) Slide the latch clip toward the fuel rail whilelifting with the screwdriver.

(6) Remove the latch clip from fuel rail.

Fig. 16 Latch Clip Location—Typical

Fig. 17 Latch Clip Removal—Typical

Fig. 18 Fuel Line Disconnection—Typical


(7) Insert special fuel line removal tool (Snap-Onnumber FIH 9055-1 or equivalent) into the fuel line(Fig. 18). Use this tool to release the locking fingersin the end of the line.

(8) With the special tool still inserted, pull the fuelline from the fuel rail.

After disconnection, the locking fingers will remainwithin the quick-connect fitting at the end of the fuelline.

(9) Inspect fuel line fitting, locking fingers and fuelrail fitting for damage. Replace as necessary.

(10) Prior to connecting the fuel line to the fuelrail, check condition of both fittings. Clean the partswith a lint-free cloth. Lubricate them with clean en-gine oil.

(11) Insert the fuel line onto the fuel rail until aclick is felt.

(12) Verify a locked condition by firmly pulling onfuel line and fitting (15-30 lbs.).

(13) Install latch clip (snaps into position). If thelatch clip will not fit, this indicates the fuel lineis not properly installed to the fuel rail. Re-check the fuel line connection.

(14) Connect negative battery cable to battery.(15) Start engine and check for leaks.


FUEL TANKS

INDEX

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Fuel Gauge Sending Unit . . . . . . . . . . . . . . . . . . . 14Fuel Pump—Removal/Installation . . . . . . . . . . . . . 14Fuel Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Fuel Tank Capacities . . . . . . . . . . . . . . . . . . . . . . . 12Fuel Tank Filler Tube Cap . . . . . . . . . . . . . . . . . . . 12

Fuel Tank Pressure Relief/Rollover Valve . . . . . . . . 14General Information . . . . . . . . . . . . . . . . . . . . . . . 12Heat Shields . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12No-Lead Fuel Tank Filler Tube . . . . . . . . . . . . . . . . 12

GENERAL INFORMATIONThese vehicles pass a full 360 degree rollover test

without fuel leakage. To accomplish this, fuel and va-por flow controls are required for all fuel tank con-nections.

All models are equipped with a pressure relief/roll-over valve mounted in the top of the fuel pump mod-ule.

An evaporative control system prevents raw fuelvapor from escaping into the atmosphere. Fuel va-pors from the fuel tank are collected in the EVAPcanister. When the engine is operating, the vaporsare drawn into the intake manifold to be used incombustion. Refer to Group 25, Emission ControlSystem for more information.

Inspect all hose/tube connections for completeness.Be sure that leaks are not present. Replace any hosethat is cracked, scuffed, swelled, has rubbed againstother vehicle components or shows any other sign ofwear that could lead to failure. If it is necessary toreplace a hose, only hose marked EFM/EFI may beused.

When installing hoses, be sure that they are routedaway from contact with other vehicle components.

The hose clamps used on fuel injected vehicles areof a special rolled edge construction to prevent theedge of the clamp from cutting into the hose. Onlythese rolled edge type clamps may be used on thissystem. Other types of clamps may cut into the hosesand cause high-pressure fuel leaks.

NO-LEAD FUEL TANK FILLER TUBEThese vehicles are designed to operate using Un-

leaded fuels. The diameter of the opening in the fueltank filler neck is sized to only accept unleaded fuelnozzles. Gasoline station pumps for unleaded andleaded fuels have different size nozzles. Leaded fuelnozzles are larger in diameter than unleaded nozzles.The fuel tank filler neck opening is also equippedwith a deflector, which the smaller unleaded nozzlepushes back upon entering the filler neck. The deflec-tor will prevent the larger diameter leaded fuel noz-zles from entering the filler neck and will deflect fuelaway from the filler neck. This happens if filling ofthe tank with leaded fuel is attempted.

A label is attached to the instrument panel underthe fuel gauge that reads UNLEADED FUEL ONLYas a reminder to the driver. A similar label is locatednear the fuel tank filler.

FUEL TANK FILLER TUBE CAPThe loss of any fuel or vapor out of the filler neck

is prevented by the use of a safety filler cap. Thiswill release only under pressure of 10.9 to 13.45 kPa(1.58 to 1.95 psi). The vacuum release is between .97and 2.0 kPa (.14 and .29 psi). This cap must be re-placed by a similar unit if replacement is necessary.

CAUTION: Remove fuel tank filler tube cap prior toremoving or repairing fuel lines to relieve fuel tankpressure.

HEAT SHIELDSThe sheet metal heat shields may have to be re-

moved when servicing the fuel tank, fuel lines or va-por vent line. The heat shields must be installed toprotect the lines and tank from the heat of the ex-haust system. Refer to Group 11, Exhaust Systemand Intake Manifold for proper installation.

FUEL TANK CAPACITIESRefer to the Specifications section at the end of the

Fuel System Group.

FUEL TANK

WARNING: THE FUEL SYSTEM IS UNDER CON-STANT FUEL PRESSURE EVEN WITH THE ENGINEOFF. THIS PRESSURE MUST BE RELEASED BE-FORE SERVICING FUEL TANK.

REMOVAL(1) Disconnect negative battery cable at battery.(2) Release fuel system pressure. Refer to the Fuel

System Pressure Release Procedure in the Fuel De-livery section of this group.

(3) Raise and support vehicle.

14 - 12 FUEL TANKS ZJ

(4) Remove the fuel tank filler hose and vent hoseretaining clamps (Fig. 1). Remove both tubes at fuelfiller tube (Fig. 1).

(5) Remove the rear tow hooks (if equipped).(6) Remove the fuel tank skid plate mounting nuts/

bolts and remove skid plate (Fig. 2) (if equipped).(7) Remove the optional trailer hitch (if equipped).(8) Remove the exhaust tailpipe heat shield mount-

ing bolts and remove shield.

CAUTION: To protect the fuel tank from exhaustheat, this shield must reinstalled after tank installa-tion.

(9) Place a hydraulic jack to bottom of fuel tank.

WARNING: PLACE A SHOP TOWEL AROUND FUELLINES TO CATCH ANY EXCESS FUEL.

(10) Disconnect fuel supply line at inlet side of fuelfilter. Disconnect fuel vent line near front of tank.Refer to Fuel Tubes/Lines/Hoses and Clamps in thisgroup. Also refer to Quick-Connect Fittings for proce-dures.

(11) Disconnect fuel pump module electrical con-nector near front of tank.

CAUTION: The right (passenger side) of the fueltank must be lowered first to gain access to the twofuel filler hose clamps located on the left side oftank (Fig. 2).

(12) Remove the two fuel tank strap nuts (Fig. 2).Position both tank support straps away from tank.

(13) Carefully lower right side of tank while feed-ing fuel hoses through access hole in body (Fig. 2)until fuel tank filler hose clamps can be removed.

(14) Before removing fuel filler hoses (Fig. 2) fromtank, mark their rotational position in relation totank. Remove both hose clamps and hoses at tank(Fig. 2). Insert the drain hose (from an approved gas-oline draining station) into either of the hose open-ings. Drain tank until empty.

(15) Continue lowering tank and remove from ve-hicle.

(16) If tank is to be replaced, disconnect fuel tankpressure relief/rollover valve (Fig. 2) from tank. Forvalve removal, refer to Fuel Tank Pressure Relief/Rollover Valve in this section. Remove fuel pumpmodule from tank. Refer to Fuel Pump Module Re-moval/Installation in the Fuel Delivery section of thisgroup.

INSTALLATION(1) Install fuel pump module and pressure relief/

rollover valve to tank (if removed).(2) Connect the fuel filter-to-fuel pump module

supply line to the fuel pump module. Refer to FuelTubes/Lines/Hoses and Clamps in this group. Also re-fer to Quick-Connect Fittings for procedures.

(3) Install fuel filler hoses and hose clamps (Fig. 2)to tank noting their previously marked position.

(4) Position fuel tank to hydraulic jack.

Fig. 1 Fuel Filler Tube and Hoses

Fig. 2 Fuel Tank Mounting

ZJ FUEL TANKS 14 - 13

(5) Raise tank into position while guiding the fuelfiller hoses into and through the access hole (Fig. 2)in body.

(6) Continue raising tank until positioned to body.(7) Attach two fuel tank mounting straps and

mounting nuts.

CAUTION: The two mounting nuts must be tight-ened until 80 mm (3.149 in.) is attained between theend of the mounting bolt and bottom of strap. Seeinsert (Fig. 2). Do not over tighten nuts.

(8) Connect pump module electrical connector.(9) Install exhaust tailpipe heat shield.(10) Connect the fuel filter-to-fuel pump module

supply line to the fuel filter. Refer to Fuel Tubes/Lines/Hoses and Clamps in this group. Also refer toQuick-Connect Fittings for procedures.

(11) Install the fuel tank skid plate (Fig. 2) andtrailer hitch (if equipped).

(12) Install the rear tow hooks (if equipped).(13) Install the fuel tank filler hose and vent hose

to tank necks. Tighten both retaining clamps (Fig. 1).(14) Lower vehicle and connect battery cable to

battery.

FUEL PUMP—REMOVAL/INSTALLATIONThe electric fuel pump is not serviceable. If it

needs replacement, the complete fuel pump modulemust be replaced. Refer to Fuel Pump Module in theFuel Delivery System section of this group.

FUEL GAUGE SENDING UNITThe fuel gauge sending unit is not serviceable. If it

needs replacement, the complete fuel pump modulemust be replaced. Refer to Fuel Pump Module in theFuel Delivery System section of this group.

FUEL TANK PRESSURE RELIEF/ROLLOVER VALVEThe fuel tank is equipped with a pressure relief/

rollover valve (Fig. 3). The dual function valve willrelieve fuel tank pressure and prevent fuel flowthrough the fuel tank vent tubes in the event of ac-cidental vehicle rollover.

The valve consists of a plunger, spring and orifice/guide plate (Fig. 4). The valve is normally open al-lowing fuel vapor to vent to the EVAP canister. Hereit is stored until it can be consumed by the engine(under controlled conditions). The plunger seats inthe guide plate at the orifice preventing liquid fuelfrom reaching the EVAP canister. This is done if bot-tom of plunger is contacted by fuel sloshing in tankwhen vehicle is cornering.

In the event of accidental vehicle rollover, the valveis inverted. In this position the plunger is forcedagainst the guide plate and raw fuel is preventedfrom flowing through the valve orifice into the fueltank vent tube.

REMOVAL(1) Disconnect negative battery cable.(2) Drain and remove the fuel tank. Refer to Fuel

Tank removal and installation in the Fuel Tank sec-tion of this group.

(3) The valve is seated in a grommet. Remove byprying one side upward and then roll the grommetout of tank.

INSTALLATION(1) Start one side of grommet into opening in fuel

tank. Using finger pressure only, press valve/grom-met into place.

(2) Install fuel tank. Refer to Fuel Tank Installa-tion.

(3) Fill fuel tank. Install fuel tank filler cap.(4) Connect negative battery cable.(5) Start vehicle and check for leaks.

Fig. 3 Pressure Relief/Rollover Valve Location

Fig. 4 Pressure Relief/Rollover Valve Operation

14 - 14 FUEL TANKS ZJ

ACCELERATOR PEDAL AND THROTTLE CABLE

GENERAL INFORMATIONThe accelerator pedal is connected to the throttle

body linkage by the throttle cable. The cable is pro-tected by a plastic sheathing and is connected to thethrottle body linkage by a ball socket (4.0L engine) orpin (5.2L engine). It is connected to the acceleratorpedal arm by a plastic retainer (clip) (Fig. 1). This re-tainer (clip) snaps into the top of the acceleratorpedal arm. Retainer tabs (built into the cable sheath-ing) (Fig. 1) fasten the cable to the dash panel.

Dual throttle return springs (attached to the throt-tle shaft) are used to close the throttle.

CAUTION: Never attempt to remove or alter thesesprings.

ACCELERATOR PEDAL

CAUTION: Be careful not to damage or kink the ca-ble core wire (within the cable sheathing) while ser-vicing accelerator pedal or throttle cable.

REMOVAL(1) From inside the vehicle, hold up accelerator

pedal. Remove plastic cable retainer (clip) and throt-tle cable core wire from upper end of pedal arm (Fig.1). Plastic cable retainer (clip) snaps into pedal arm.

(2) Remove accelerator pedal bracket nuts. Removeaccelerator pedal assembly (Fig. 1).

INSTALLATION(1) Place accelerator pedal assembly over studs

protruding from floor pan. Tighten mounting nuts to10 Nzm (92 in. lbs.) torque.

(2) Slide throttle cable into opening in top of pedalarm. Push plastic cable retainer (clip) into pedal armopening until it snaps into place.

(3) Before starting engine, operate acceleratorpedal to check for any binding.

THROTTLE CABLE

REMOVAL(1) From inside the vehicle, hold up accelerator

pedal. Remove plastic cable retainer (clip) and throt-tle cable core wire from upper end of pedal arm (Fig.1). Plastic cable retainer (clip) snaps into pedal arm.

(2) Remove the cable core wire at pedal arm.(3) From inside the vehicle, pinch both sides of the

cable housing retainer tabs (Fig. 1) at the dashpanel. Remove cable housing from dash panel andpull into the engine compartment.

(4) 4.0L Engine: Remove cable from clip on enginevalve cover (Fig. 2) and clip at dash panel.

(5) Remove the throttle cable ball end socket atthrottle body linkage (Figs. 2 or 3) (snaps off).

(6) 4.0L Engine: Remove throttle cable from throt-tle body mounting bracket by compressing retainertabs and pushing cable through hole in bracket. Re-move throttle cable from vehicle.

Fig. 1 Accelerator Pedal Mounting—Typical

Fig. 2 Throttle Cable—4.0L Engine

ZJ ACCELERATOR PEDAL AND THROTTLE CABLE 14 - 15

(7) 5.2L Engine: Remove cable housing at throttlebody mounting bracket by pressing forward on re-lease tab with a small screwdriver (Fig. 4). To pre-vent cable housing breakage, press on the tabonly enough to release the cable from thebracket. Lift the cable housing straight up frombracket while pressing on release tab. Remove throt-tle cable from vehicle.INSTALLATION

(1) 4.0L Engine: Slide throttle cable through holein throttle body bracket until retainer tabs lock intobracket. Connect cable ball end to throttle body link-age ball (snaps on).

(2) 5.2L Engine: Connect cable ball end to throttlebody linkage ball (snaps on). Connect cable to throt-tle body bracket (push down and lock).

(3) 4.0L Engine: Snap cable into clip on enginevalve cover and clip at dash panel.

(4) Push other end of cable through opening indash panel until retaining tabs lock into panel.

(5) From inside drivers compartment, slide throttlecable core wire into opening in top of pedal arm.Push cable retainer (clip) into pedal arm opening un-til it snaps in place.

(6) Before starting engine, operate acceleratorpedal to check for any binding.

Fig. 3 Throttle Cable—5.2L V-8 Engine Fig. 4 Cable Release Tab—5.2L Engines—Typical

14 - 16 ACCELERATOR PEDAL AND THROTTLE CABLE ZJ

MULTI-PORT FUEL INJECTION (MFI)—4.0L 6 CYL. ENGINE—COMPONENTDESCRIPTION/SYSTEM OPERATION

INDEX

page page

Air Conditioning (A/C) Clutch Relay—PCM Output . 23Air Conditioning (A/C) Controls—PCM Input . . . . . . 19Auto Shutdown (ASD) Relay—PCM Output . . . . . . 23Automatic Shutdown (ASD) Sense—PCM Input . . . 19Battery Voltage—PCM Input . . . . . . . . . . . . . . . . . 19Brake Switch—PCM Input . . . . . . . . . . . . . . . . . . . 19Camshaft Position Sensor—PCM Input . . . . . . . . . 19Crankshaft Position Sensor—PCM Input . . . . . . . . 20Data Link Connector—PCM Input . . . . . . . . . . . . . 19Data Link Connector—PCM Output . . . . . . . . . . . . 24Duty Cycle Evap Purge Solenoid—PCM Output . . . 24Engine Coolant Temperature Sensor—PCM Input . 21Fuel Injectors—PCM Output . . . . . . . . . . . . . . . . . 24Fuel Pressure Regulator . . . . . . . . . . . . . . . . . . . . 28Fuel Rail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28General Information . . . . . . . . . . . . . . . . . . . . . . . 17Generator Field—PCM Output . . . . . . . . . . . . . . . . 24Generator Lamp—PCM Output . . . . . . . . . . . . . . . 24Idle Air Control (IAC) Motor—PCM Output . . . . . . . 23Ignition Circuit Sense—PCM Input . . . . . . . . . . . . . 21Ignition Coil—PCM Output . . . . . . . . . . . . . . . . . . . 25

Intake Manifold Air Temperature Sensor—PCMInput . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Malfunction Indicator Lamp—PCM Output . . . . . . . 24Manifold Absolute Pressure (MAP) Sensor—PCM

Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Open Loop/Closed Loop Modes of Operation . . . . . 25Oxygen (O2S) Sensor—PCM Input . . . . . . . . . . . . 21Park/Neutral Switch—PCM Input . . . . . . . . . . . . . . 21Power Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Powertrain Control Module (PCM) . . . . . . . . . . . . . 18SCI Receive—PCM Input . . . . . . . . . . . . . . . . . . . 22SCI Transmit—PCM Output . . . . . . . . . . . . . . . . . . 25Sensor Return—PCM Input . . . . . . . . . . . . . . . . . . 22Shift Indicator—PCM Output . . . . . . . . . . . . . . . . . 25Speed Control—PCM Input . . . . . . . . . . . . . . . . . . 22Speed Control—PCM Output . . . . . . . . . . . . . . . . . 25Tachometer—PCM Output . . . . . . . . . . . . . . . . . . . 25Throttle Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Throttle Position Sensor (TPS)—PCM Input . . . . . . 22Vehicle Speed Sensor—PCM Input . . . . . . . . . . . . 22

GENERAL INFORMATIONAll 4.0L engines are equipped with sequential

Multi-Port Fuel Injection (MFI). The MFI systemprovides precise air/fuel ratios for all driving condi-tions.

The powertrain control module (PCM) operates thefuel system. The PCM was formerly referred to asthe SBEC or engine controller. The PCM is a pre-pro-grammed, dual microprocessor digital computer. Itregulates ignition timing, air-fuel ratio, emission con-trol devices, charging system, speed control, air con-ditioning compressor clutch engagement and idlespeed. The PCM can adapt its programming to meetchanging operating conditions.

Powertrain Control Module (PCM) Inputs rep-resent the instantaneous engine operating conditions.Air-fuel mixture and ignition timing calibrations forvarious driving and atmospheric conditions are pre-programmed into the PCM. The PCM monitors andanalyzes various inputs. It then computes engine fueland ignition timing requirements based on these in-puts. Fuel delivery control and ignition timing willthen be adjusted accordingly.

Other inputs to the PCM are provided by the brakelight switch, air conditioning select switch and thespeed control switches. All inputs to the PCM areconverted into signals.

Electrically operated fuel injectors spray fuel inprecise metered amounts into the intake port directlyabove the intake valve. The injectors are fired in a

specific sequence by the PCM. The PCM maintainsan air/fuel ratio of 14.7 to 1 by constantly adjustinginjector pulse width. Injector pulse width is thelength of time that the injector opens and sprays fuelinto the chamber. The PCM adjusts injector pulsewidth by opening and closing the ground path to theinjector.

Manifold absolute pressure (air density) and enginerpm (speed) are the primary inputs that determinefuel injector pulse width. The PCM also monitorsother inputs when adjusting air-fuel ratio.

Inputs That Effect Fuel Injector Pulse Width:• Exhaust gas oxygen content• Engine coolant temperature• Manifold absolute pressure (MAP)• Engine speed• Throttle position• Battery voltage• Air conditioning selection• Transmission gear selection (automatic transmis-sions only)• Speed control

The powertrain control module (PCM) adjusts igni-tion timing by controlling ignition coil operation. Theignition coil receives battery voltage when the igni-tion key is in the run or starter position. The PCMprovides a ground for the ignition coil. The coil dis-charges when the PCM supplies a ground. By switch-ing the ground path on and off, the PCM regulatesignition timing.

ZJ FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—4.0L 6 CYL. ENGINE 14 - 17

The sensors and switches that provide inputs tothe powertrain control module (PCM) comprise theEngine Control System. It is also comprised of thePCM Outputs (engine control devices that the are op-erated by the PCM).

SYSTEM DIAGNOSISThe powertrain control module (PCM) tests many

of its own input and output circuits. If a DiagnosticTrouble Code (DTC) is found in a major system, thisinformation is stored in the PCM memory. Refer toOn-Board Diagnostics in the MFI System—4.0L En-gine—General Diagnosis section of this group forDTC information.

POWERTRAIN CONTROL MODULE (PCM)The powertrain control module (PCM) (Fig. 1) oper-

ates the fuel system. The PCM was formerly referredto as the SBEC or engine controller. The PCM is apre-programmed, dual microprocessor digital com-puter. It regulates ignition timing, air-fuel ratio,emission control devices, charging system, speed con-trol, air conditioning compressor clutch engagementand idle speed. The PCM can adapt its programmingto meet changing operating conditions.

The PCM receives input signals from variousswitches and sensors. Based on these inputs, thePCM regulates various engine and vehicle operationsthrough different system components. These compo-nents are referred to as powertrain control module(PCM) outputs. The sensors and switches that pro-vide inputs to the PCM are considered powertraincontrol module (PCM) inputs.

The PCM adjusts ignition timing based upon in-puts it receives from sensors that react to: enginerpm, manifold absolute pressure, engine coolant tem-perature, throttle position, transmission gear selec-tion (automatic transmission), vehicle speed and thebrake switch.

The PCM adjusts idle speed based on inputs it re-ceives from sensors that react to: throttle position,vehicle speed, transmission gear selection, enginecoolant temperature and from inputs it receives fromthe air conditioning clutch switch and brake switch.

Based on inputs that it receives, the PCM adjustsignition coil dwell. The PCM also adjusts the gener-ator charge rate through control of the generatorfield and provides speed control operation.

Powertrain Control Module (PCM) Inputs:• Generator output• A/C request (if equipped with factory A/C)• A/C select (if equipped with factory A/C)• Auto shutdown (ASD) sense• Intake manifold air temperature sensor• Battery voltage• Brake switch• Engine coolant temperature sensor• Crankshaft position sensor• Ignition circuit sense (ignition switch in run posi-tion)• Manifold absolute pressure sensor• Overdrive/override switch• Oxygen sensor• Park/neutral switch (auto. trans. only)• SCI receive (DRB scan tool connection)• Speed control resume switch• Speed control set switch• Speed control on/off switch• Camshaft position sensor signal• Throttle position sensor• Vehicle speed sensor• Sensor return• Power ground• Signal ground

Powertrain Control Module (PCM) Outputs:• A/C clutch relay• Idle air control (IAC) motor• Auto shutdown (ASD) relay• Generator field• Malfunction indicator lamp (Check engine lamp)• Fuel injectors• Fuel pump relay• Ignition coil• SCI transmit (DRB scan tool connection)• Shift indicator lamp (manual transmission only)• Speed control vacuum solenoid• Speed control vent solenoid• Tachometer (on instrument panel, if equipped)

The powertrain control module (PCM) contains avoltage convertor. This converts battery voltage to a

Fig. 1 Powertrain Control Module (PCM)

14 - 18 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—4.0L 6 CYL. ENGINE ZJ

regulated 8.0 volts. It is used to power the crankshaftposition sensor, camshaft position sensor and vehiclespeed sensor. The PCM also provides a five (5) voltsupply for the manifold absolute pressure (MAP) sen-sor and throttle position sensor (TPS).

AIR CONDITIONING (A/C) CONTROLS—PCM INPUTThe A/C control system information applies to fac-

tory installed air conditioning units.A/C SELECT SIGNAL: When the A/C switch is in

the ON position and the A/C low-pressure switch isclosed, an input signal is sent to the powertrain con-trol module (PCM). The signal informs the PCM thatA/C has been selected. The PCM then adjusts idlespeed to a pre-programmed rpm through the idle aircontrol (IAC) motor to compensate for increased en-gine load.

A/C REQUEST SIGNAL: Once A/C has been se-lected, the powertrain control module (PCM) receivesthe A/C request signal from the evaporator switch.The input indicates that the evaporator temperatureis in the proper range for A/C application. The PCMuses this input to cycle the A/C compressor clutchthrough the A/C relay. It will also determine the cor-rect engine idle speed through the idle air control(IAC) motor position.

If the A/C low-pressure switch opens (indicating alow refrigerant level), the PCM will not receive anA/C select signal. The PCM will then remove theground from the A/C relay. This will deactivate theA/C compressor clutch.

If the evaporator switch opens, indicating thatevaporator is not in proper temperature range, thePCM will not receive the A/C request signal. ThePCM will then remove the ground from the A/C relay,deactivating the A/C compressor clutch.

AUTOMATIC SHUTDOWN (ASD) SENSE—PCMINPUT

A 12 volt signal at this input indicates to the PCMthat the ASD has been activated. The ASD relay islocated in the power distribution center (PDC) in theengine compartment. It is used to connect the oxygensensor heater element, ignition coil, generator fieldwinding and fuel injectors to 12 volt + power supply.

This input is used only to sense that the ASD relayis energized. If the powertrain control module (PCM)does not see 12 volts at this input when the ASDshould be activated, it will set a Diagnostic TroubleCode (DTC).

BATTERY VOLTAGE—PCM INPUTThe battery voltage input provides power to the

powertrain control module (PCM). It also informs thePCM what voltage level is supplied to the ignitioncoil and fuel injectors.

If battery voltage is low, the PCM will increase in-jector pulse width (period of time that the injector isenergized). This is done to compensate for the re-duced flow through the injector caused by the low-ered voltage.

BRAKE SWITCH—PCM INPUTWhen the brake light switch is activated, the pow-

ertrain control module (PCM) receives an input indi-cating that the brakes are being applied. Afterreceiving this input, the PCM maintains idle speed toa scheduled rpm through control of the idle air con-trol (IAC) motor. The brake switch input is also usedto operate the speed control system.

CAMSHAFT POSITION SENSOR—PCM INPUTA sync signal is provided by the camshaft position

sensor located in the distributor (Fig. 2). The syncsignal from this sensor works in conjunction with thecrankshaft position sensor to provide the powertraincontrol module (PCM) with inputs. This is done to es-tablish and maintain correct injector firing order.

Refer to Camshaft Position Sensor in Group 8D, Ig-nition System for more information.

DATA LINK CONNECTOR—PCM INPUTThe data link connector (diagnostic scan tool con-

nector) links the DRB scan tool with the powertraincontrol module (PCM). The data link connector is lo-cated in the engine compartment (Fig. 3). For opera-tion of the DRB scan tool, refer to the appropriatePowertrain Diagnostic Procedures service manual.

The data link connector uses two different pins onthe PCM. One is for Data Link Transmit and theother is for Data Link Receive.

INTAKE MANIFOLD AIR TEMPERATURE SENSOR—PCM INPUT

The intake manifold air temperature sensor is in-stalled in the intake manifold with the sensor ele-

Fig. 2 Camshaft Position Sensor—Typical


ment extending into the air stream (Fig. 4). Thesensor provides an input voltage to the powertraincontrol module (PCM) indicating intake manifold airtemperature. The input is used along with inputsfrom other sensors to determine injector pulse width.As the temperature of the air-fuel stream in themanifold varies, the sensor resistance changes. Thisresults in a different input voltage to the PCM.

CRANKSHAFT POSITION SENSOR—PCM INPUTThis sensor is a hall effect device that detects

notches in the flywheel (manual transmission), orflexplate (automatic transmission).

This sensor is used to indicate to the powertraincontrol module (PCM) that a spark and or fuel injec-tion event is to be required. The output from thissensor, in conjunction with the camshaft position sen-

sor signal, is used to differentiate between fuel injec-tion and spark events. It is also used to synchronizethe fuel injectors with their respective cylinders.

The sensor is bolted to the transmission housingnear the rear of the cylinder head (Figs. 5 or 6).

Refer to Group 8D, Ignition System for more crank-shaft position sensor information.

The engine will not operate if the PCM does not re-ceive a crankshaft position sensor input.

Fig. 3 Data Link Connector Location—Typical

Fig. 4 Air Temperature Sensor

Fig. 5 Crankshaft Position Sensor—4.0L EngineWith Man. Trans.

Fig. 6 Crankshaft Position Sensor—4.0L EngineWith Auto. Trans.


ENGINE COOLANT TEMPERATURE SENSOR—PCMINPUT

The engine coolant temperature sensor is installedin the thermostat housing (Fig. 7) and protrudes intothe water jacket. The sensor provides an input volt-age to the powertrain control module (PCM) relatingengine coolant temperature. The PCM uses this in-put along with inputs from other sensors to deter-mine injector pulse width and ignition timing. Ascoolant temperature varies, the coolant temperaturesensor’s resistance changes. The change in resistanceresults in a different input voltage to the PCM.

When the engine is cold, the PCM will operate inOpen Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is doneuntil normal operating temperatures are reached.

IGNITION CIRCUIT SENSE—PCM INPUTThe ignition circuit sense input tells the powertrain

control module (PCM) the ignition switch has ener-gized the ignition circuit. Refer to the wiring dia-grams for circuit information.

MANIFOLD ABSOLUTE PRESSURE (MAP)SENSOR—PCM INPUT

The MAP sensor reacts to absolute pressure in theintake manifold. It provides an input voltage to thepowertrain control module (PCM). As engine loadchanges, manifold pressure varies. The change inmanifold pressure causes MAP sensor voltage tochange. The change in MAP sensor voltage results ina different input voltage to the PCM. The input volt-age level supplies the PCM with information aboutambient barometric pressure during engine start-up(cranking) and engine load while the engine is run-ning. The PCM uses this input along with inputsfrom other sensors to adjust air-fuel mixture.

The MAP sensor is mounted on the dash panel(Fig. 8). The sensor is connected to the throttle bodywith a vacuum hose and to the PCM electrically.

OXYGEN (O2S) SENSOR—PCM INPUTThe O2S sensor is located in the exhaust down pipe

(Fig. 9). It provides an input voltage to the power-train control module (PCM) relating the oxygen con-tent of the exhaust gas. The PCM uses thisinformation to fine tune the air-fuel ratio by adjust-ing injector pulse width.

The O2S sensor produces voltages from 0 to 1 volt.This voltage will depend upon the oxygen content ofthe exhaust gas in the exhaust manifold. When alarge amount of oxygen is present (caused by a leanair-fuel mixture), the sensor produces a low voltage.When there is a lesser amount present (rich air-fuelmixture) it produces a higher voltage. By monitoringthe oxygen content and converting it to electricalvoltage, the sensor acts as a rich-lean switch.

The oxygen sensor is equipped with a heating ele-ment that keeps the sensor at proper operating tem-perature during all operating modes. Maintainingcorrect sensor temperature at all times allows thesystem to enter into closed loop operation sooner.

In Closed Loop operation, the powertrain controlmodule (PCM) monitors the O2S sensor input (alongwith other inputs). It then adjusts the injector pulsewidth accordingly. During Open Loop operation, thePCM ignores the O2S sensor input and adjusts injec-tor pulse width to a preprogrammed value (based onother sensor inputs).

PARK/NEUTRAL SWITCH—PCM INPUTThe park/neutral switch is located on the transmis-

sion housing and provides an input to the powertraincontrol module (PCM). This will indicate that the au-tomatic transmission is in Park, Neutral or a drivegear selection. This input is used to determine idlespeed (varying with gear selection), fuel injectorpulse width, ignition timing advance and vehiclespeed control operation. Refer to Group 21, Transmis-sions, for testing, replacement and adjustment infor-mation.

Fig. 7 Coolant Temperature Sensor

Fig. 8 Manifold Absolute Pressure (MAP) Sensor


POWER GROUNDThe power ground is used to control ground circuits

for the following powertrain control module (PCM)loads:• Generator Field Winding• 8 volt (PCM) power supply• Fuel Injectors• Ignition Coil

SCI RECEIVE—PCM INPUTSCI Receive is the serial data communication re-

ceive circuit for the DRB scan tool. The powertraincontrol module (PCM) receives data from the DRBthrough the SCI Receive circuit.

SPEED CONTROL—PCM INPUTThe speed control system provides three separate

inputs to the powertrain control module (PCM); On/Off, Set and Resume. The On/Off input informs thePCM that the speed control system has been acti-vated. The Set input informs the PCM that a fixedvehicle speed has been selected. The Resume inputindicates to the PCM that the previous fixed speed isrequested.

The speed control operating range is from 50 km/hto 142 km/h (35 to 85 mph). Inputs that effect speedcontrol operation are:• Brake switch position• Park/neutral switch• Vehicle speed sensor• Throttle position sensor

Refer to Group 8H for further speed control infor-mation.

SENSOR RETURN—PCM INPUTSensor Return provides a low noise ground refer-

ence for all system sensors.

THROTTLE POSITION SENSOR (TPS)—PCM INPUTThe throttle position sensor (TPS) is mounted on

the throttle body (Fig. 10). The TPS is a variable re-sistor that provides the powertrain control module(PCM) with an input signal (voltage) that representsthrottle blade position. The sensor is connected to thethrottle blade shaft. As the position of the throttleblade changes, the resistance of the TPS changes.

The PCM supplies approximately 5 volts to theTPS. The TPS output voltage (input signal to thePCM) represents the throttle blade position. ThePCM receives an input signal voltage from the TPS.This will vary in an approximate range of from 1 voltat minimum throttle opening (idle), to 4 volts at wideopen throttle. Along with inputs from other sensors,the PCM uses the TPS input to determine currentengine operating conditions. In response to engineoperating conditions, the PCM will adjust fuel injec-tor pulse width and ignition timing.

VEHICLE SPEED SENSOR—PCM INPUTThe speed sensor (Fig. 11) is located in the exten-

sion housing of the transmission (2WD) or on thetransfer case extension housing (4WD). The sensorinput is used by the powertrain control module(PCM) to determine vehicle speed and distance trav-eled.

The speed sensor generates 8 pulses per sensorrevolution. These signals, in conjunction with aclosed throttle signal from the throttle position sen-sor, indicate a closed throttle deceleration to thePCM. When the vehicle is stopped at idle, a closedthrottle signal is received by the PCM (but a speedsensor signal is not received).

Under deceleration conditions, the PCM adjusts theidle air control (IAC) motor to maintain a desiredMAP value. Under idle conditions, the PCM adjuststhe IAC motor to maintain a desired engine speed.

Fig. 9 Heated Oxygen Sensor Location

Fig. 10 Throttle Position Sensor and IAC Motor


AIR CONDITIONING (A/C) CLUTCH RELAY—PCMOUTPUT

The powertrain control module (PCM) activates theA/C compressor through the A/C clutch relay. ThePCM regulates A/C compressor operation by switch-ing the ground circuit for the A/C clutch relay on andoff. The relay is located in the power distributioncenter (PDC) (Fig. 12). For the location of the relaywithin the PDC, refer to label under PDC cover.

When the PCM receives a request for A/C from theA/C evaporator switch, it will adjust idle air control(IAC) motor position. This is done to increase idlespeed. The PCM will then activate the A/C clutchthrough the A/C clutch relay. The PCM then adjuststhe idle air control (IAC) stepper motor position tocompensate for increased engine load from the A/Ccompressor.

By switching the ground path for the relay on andoff, the PCM is able to cycle the A/C compressorclutch. This is based on changes in engine operatingconditions. If, during A/C operation, the PCM senseslow idle speeds or a wide open throttle condition, itwill de-energize the relay. This prevents A/C clutchengagement. The relay will remain de-energized untilthe idle speed increases or the wide open throttlecondition exceeds 15 seconds, or no longer exists. ThePCM will also de-energize the relay if engine coolanttemperature exceeds 125°C (257°F).

IDLE AIR CONTROL (IAC) MOTOR—PCM OUTPUTThe IAC motor is mounted on the throttle body

(Fig. 10) and is controlled by the powertrain controlmodule (PCM).

The throttle body has an air control passage thatprovides air for the engine at idle (the throttle plateis closed). The IAC motor pintle protrudes into theair control passage and regulates air flow through it.Based on various sensor inputs, the powertrain con-trol module (PCM) adjusts engine idle speed by mov-ing the IAC motor pintle in and out of the air controlpassage. The IAC motor is positioned when the igni-tion key is turned to the On position.

A (factory adjusted) set screw is used to mechani-cally limit the position of the throttle body throttleplate. Never attempt to adjust the engine idlespeed using this screw. All idle speed functions arecontrolled by the PCM.

AUTO SHUTDOWN (ASD) RELAY—PCM OUTPUTThe ASD relay is located in the power distribution

center (PDC) (Fig. 12). For the location of this relaywithin the PDC, refer to label under PDC cover.

The ASD supplies battery voltage to the fuel pump,fuel injector, ignition coil, generator field windingand oxygen (O2S) sensor heating element. Theground circuit for the coil in the ASD relay is con-trolled by the powertrain control module (PCM). ThePCM operates the relay by switching the ground cir-cuit on and off.

The fuel pump relay is controlled by the PCMthrough same circuit that the ASD relay is con-trolled.

Fig. 11 Vehicle Speed Sensor—Typical

Fig. 12 Power Distribution Center (PDC)


DUTY CYCLE EVAP PURGE SOLENOID—PCMOUTPUT

4.0L ENGINE—CALIFORNIA EMISSIONPACKAGE ONLY

The duty cycle EVAP purge solenoid is located inthe engine compartment near the windshield washerreservoir tank (Fig. 13).

The duty cycle EVAP purge solenoid regulates therate of vapor flow from the EVAP canister to the in-take manifold. The powertrain control module oper-ates the solenoid.

During the cold start warm-up period and the hotstart time delay, the PCM does not energize the sole-noid. When de-energized, no vapors are purged.

The engine enters closed loop operation after itreaches a specified temperature and the programmedtime delay ends. During closed loop operation, thePCM energizes and de-energizes the solenoid 5 to 10times per second, depending upon operating condi-tions. The PCM varies the vapor flow rate by chang-ing solenoid pulse width. Pulse width is the amountof time the solenoid is energized.

Refer to Group 25, Emission Control System for ad-ditional information.

GENERATOR FIELD—PCM OUTPUTThe powertrain control module (PCM) regulates the

charging system voltage within a range of 12.9 to15.0 volts. Refer to Group 8A for charging system in-formation.

GENERATOR LAMP—PCM OUTPUTIf the powertrain control module (PCM) senses a

low charging condition in the charging system, it willilluminate the generator lamp on the instrumentpanel. For example, during low idle with all accesso-ries turned on, the lamp may momentarily go on.Once the PCM corrects idle speed to a higher rpm,the lamp will go out. Refer to Group 8A for chargingsystem information.

DATA LINK CONNECTOR—PCM OUTPUTRefer to the previous paragraphs on Data Link

Connector—PCM Input for information.

FUEL INJECTORS—PCM OUTPUTSix fuel injectors are attached to the fuel rail (Fig.

14).The nozzle ends of the injectors are positioned into

openings in the intake manifold just above the intakevalve ports of the cylinder head. The engine wiringharness connector for each fuel injector is equippedwith an attached numerical tag (INJ 1, INJ 2 etc.).This is used to identify each fuel injector.

The injectors are energized individually in a se-quential order by the powertrain control module(PCM). The PCM will adjust injector pulse width byswitching the ground path to each individual injectoron and off. Injector pulse width is the period of timethat the injector is energized. The PCM will adjustinjector pulse width based on various inputs it re-ceives.

During start up, battery voltage is supplied to theinjectors through the ASD relay. When the engine isoperating, voltage is supplied by the charging sys-tem. The PCM determines injector pulse width basedon various inputs.

MALFUNCTION INDICATOR LAMP—PCM OUTPUTThe malfunction indicator lamp illuminates each

time the ignition key is turned on. It will stay on forapproximately three seconds as a bulb test. The lamp

Fig. 13 Purge Solenoid—4.0L Engine—CaliforniaEmission Package

Fig. 14 Fuel Injectors—Typical


is displayed on the instrument panel as the CHECKENGINE lamp (Fig. 15).

If the powertrain control module (PCM) receives anincorrect signal, or no signal from certain sensors oremission related systems, the lamp is turned on. Thisis a warning that the PCM has recorded a system orsensor malfunction. In some cases, when a problem isdeclared, the PCM will go into a limp-in mode. Thisis an attempt to keep the system operating. It signalsan immediate need for service.

The lamp can also be used to display a DiagnosticTrouble Code (DTC). Cycle the ignition switch On-Off-On-Off-On within three seconds and any codesstored in the PCM memory will be displayed. This isdone in a series of flashes representing digits. Referto On-Board Diagnostics in the General Diagnosissection of this group for more information.

IGNITION COIL—PCM OUTPUTSystem voltage is supplied to the ignition coil pos-

itive terminal. The powertrain control module (PCM)operates the ignition coil. Base (initial) ignitiontiming is not adjustable. The PCM adjusts ignitiontiming to meet changing engine operating conditions.

The ignition coil is located near the distributor(Fig. 16).

SCI TRANSMIT—PCM OUTPUTSCI Transmit is the serial data communication

transmit circuit for the DRB scan tool. The power-train control module (PCM) transmits data to theDRB through the SCI Transmit circuit.

SHIFT INDICATOR—PCM OUTPUTVehicles equipped with manual transmissions have

an Up-Shift indicator lamp. The lamp is controlled bythe powertrain control module (PCM). The lamp illu-minates on the instrument panel to indicate whenthe driver should shift to the next highest gear forbest fuel economy. The PCM will turn the lamp OFF

after 3 to 5 seconds if the shift of gears is not per-formed. The up-shift lamp will remain off until vehi-cle stops accelerating and is brought back to range ofup-shift lamp operation. This will also happen if ve-hicle is shifted into fifth gear.

The indicator lamp is normally illuminated whenthe ignition switch is turned on and it is turned offwhen the engine is started up. With the engine run-ning, the lamp is turned on/off depending upon en-gine speed and load.

SPEED CONTROL—PCM OUTPUTSpeed control operation is regulated by the power-

train control module (PCM). The PCM controls thevacuum to the throttle actuator through the speedcontrol vacuum and vent solenoids. Refer to Group8H for Speed Control information.

TACHOMETER—PCM OUTPUTThe powertrain control module (PCM) supplies en-

gine rpm values to the instrument cluster tachome-ter. Refer to Group 8E for tachometer information.

OPEN LOOP/CLOSED LOOP MODES OFOPERATION

As input signals to the powertrain control module(PCM) change, the PCM adjusts its response to theoutput devices. For example, the PCM must calculatedifferent injector pulse width and ignition timing foridle than it does for wide open throttle (WOT). Thereare several different modes of operation that deter-mine how the PCM responds to the various input sig-nals.

MODES• Open Loop• Closed Loop

During Open Loop modes, the powertrain controlmodule (PCM) receives input signals and respondsonly according to preset PCM programming. Input

Fig. 15 Check Engine Lamp Location

Fig. 16 Ignition Coil—Typical


from the oxygen (O2S) sensor is not monitored dur-ing Open Loop modes.

During Closed Loop modes, the PCM will monitorthe oxygen (O2S) sensor input. This input indicatesto the PCM whether or not the calculated injectorpulse width results in the ideal air-fuel ratio. Thisratio is 14.7 parts air-to-1 part fuel. By monitoringthe exhaust oxygen content through the O2S sensor,the PCM can fine tune the injector pulse width. Thisis done to achieve optimum fuel economy combinedwith low emission engine performance.

The fuel injection system has the following modesof operation:• Ignition switch ON• Engine start-up (crank)• Engine warm-up• Idle• Cruise• Acceleration• Deceleration• Wide open throttle (WOT)• Ignition switch OFF

The ignition switch On, engine start-up (crank), en-gine warm-up, acceleration, deceleration and wideopen throttle modes are Open Loop modes. The idleand cruise modes, (with the engine at operating tem-perature) are Closed Loop modes.

IGNITION SWITCH (KEY-ON) MODEThis is an Open Loop mode. When the fuel system

is activated by the ignition switch, the following ac-tions occur:• The powertrain control module (PCM) pre-posi-tions the idle air control (IAC) motor.• The PCM determines atmospheric air pressurefrom the MAP sensor input to determine basic fuelstrategy.• The PCM monitors the engine coolant temperaturesensor input. The PCM modifies fuel strategy basedon this input.• Intake manifold air temperature sensor input ismonitored• Throttle position sensor (TPS) is monitored• The auto shutdown (ASD) relay is energized by thePCM for approximately three seconds.• The fuel pump is energized through the fuel pumprelay by the PCM. The fuel pump will operate for ap-proximately three seconds unless the engine is oper-ating or the starter motor is engaged.• The O2S sensor heater element is energizedthrough the fuel pump relay. The O2S sensor input isnot used by the PCM to calibrate air-fuel ratio dur-ing this mode of operation.• The up-shift indicator lamp is illuminated (manualtransmission only).

ENGINE START-UP MODEThis is an Open Loop mode. The following actions

occur when the starter motor is engaged.The powertrain control module (PCM) receives in-

puts from:• Battery voltage• Engine coolant temperature sensor• Crankshaft position sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Starter motor relay• Camshaft position sensor signal

The PCM monitors the crankshaft position sensor.If the PCM does not receive a crankshaft positionsensor signal within 3 seconds of cranking the en-gine, it will shut down the fuel injection system.

The fuel pump is activated by the PCM throughthe fuel pump relay.

Voltage is applied to the fuel injectors with thePCM. The PCM will then control the injection se-quence and injector pulse width by turning theground circuit to each individual injector on and off.

The PCM determines the proper ignition timing ac-cording to input received from the crankshaft posi-tion sensor.

ENGINE WARM-UP MODEThis is an Open Loop mode. During engine warm-

up, the powertrain control module (PCM) receives in-puts from:• Battery voltage• Crankshaft position sensor• Engine coolant temperature sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)• Park/neutral switch (gear indicator signal—auto.trans. only)• Air conditioning select signal (if equipped)• Air conditioning request signal (if equipped)

Based on these inputs the following occurs:• Voltage is applied to the fuel injectors with thepowertrain control module (PCM). The PCM willthen control the injection sequence and injector pulsewidth by turning the ground circuit to each individ-ual injector on and off.• The PCM adjusts engine idle speed through theidle air control (IAC) motor and adjusts ignition tim-ing.• The PCM operates the A/C compressor clutchthrough the clutch relay. This is done if A/C has beenselected by the vehicle operator and requested by theA/C thermostat.• If the vehicle has a manual transmission, the up-shift lamp is operated by the PCM.


• When the engine has reached operating tempera-ture, the PCM will begin monitoring O2S sensor in-put. The system will then leave the warm-up modeand go into closed loop operation.

IDLE MODEWhen the engine is at operating temperature, this

is a Closed Loop mode. At idle speed, the powertraincontrol module (PCM) receives inputs from:• Air conditioning select signal (if equipped)• Air conditioning request signal (if equipped)• Battery voltage• Crankshaft position sensor• Engine coolant temperature sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)• Battery voltage• Park/neutral switch (gear indicator signal—auto.trans. only)• Oxygen sensor

Based on these inputs, the following occurs:• Voltage is applied to the fuel injectors with thepowertrain control module (PCM). The PCM willthen control injection sequence and injector pulsewidth by turning the ground circuit to each individ-ual injector on and off.• The PCM monitors the O2S sensor input and ad-justs air-fuel ratio by varying injector pulse width. Italso adjusts engine idle speed through the idle aircontrol (IAC) motor.• The PCM adjusts ignition timing by increasingand decreasing spark advance.• The PCM operates the A/C compressor clutchthrough the clutch relay. This happens if A/C hasbeen selected by the vehicle operator and requestedby the A/C thermostat.

CRUISE MODEWhen the engine is at operating temperature, this

is a Closed Loop mode. At cruising speed, the power-train control module (PCM) receives inputs from:• Air conditioning select signal (if equipped)• Air conditioning request signal (if equipped)• Battery voltage• Engine coolant temperature sensor• Crankshaft position sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)• Park/neutral switch (gear indicator signal—auto.trans. only)• Oxygen (O2S) sensor

Based on these inputs, the following occurs:

• Voltage is applied to the fuel injectors with thePCM. The PCM will then adjust the injector pulsewidth by turning the ground circuit to each individ-ual injector on and off.• The PCM monitors the O2S sensor input and ad-justs air-fuel ratio. It also adjusts engine idle speedthrough the idle air control (IAC) motor.• The PCM adjusts ignition timing by turning theground path to the coil on and off.• The PCM operates the A/C compressor clutchthrough the clutch relay. This happens if A/C hasbeen selected by the vehicle operator and requestedby the A/C thermostat.

ACCELERATION MODEThis is an Open Loop mode. The powertrain control

module (PCM) recognizes an abrupt increase inthrottle position or MAP pressure as a demand forincreased engine output and vehicle acceleration. ThePCM increases injector pulse width in response to in-creased throttle opening.

DECELERATION MODEWhen the engine is at operating temperature, this

is an Open Loop mode. During hard deceleration, thepowertrain control module (PCM) receives the follow-ing inputs.• Air conditioning select signal (if equipped)• Air conditioning request signal (if equipped)• Battery voltage• Engine coolant temperature sensor• Crankshaft position sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)• Park/neutral switch (gear indicator signal—auto.trans. only)

If the vehicle is under hard deceleration with theproper rpm and closed throttle conditions, the PCMwill ignore the oxygen sensor input signal. The PCMwill enter a fuel cut-off strategy in which it will notsupply battery voltage to the injectors. If a hard de-celeration does not exist, the PCM will determine theproper injector pulse width and continue injection.

Based on the above inputs, the PCM will adjust en-gine idle speed through the idle air control (IAC) mo-tor.

The PCM adjusts ignition timing by turning theground path to the coil on and off.

The PCM opens the ground circuit to the A/Cclutch relay to disengage the A/C compressor clutch.This is done until the vehicle is no longer under de-celeration (if the A/C system is operating).


WIDE OPEN THROTTLE MODEThis is an Open Loop mode. During wide open

throttle operation, the powertrain control module(PCM) receives the following inputs.• Battery voltage• Crankshaft position sensor• Engine coolant temperature sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)

During wide open throttle conditions, the followingoccurs:• Voltage is applied to the fuel injectors with thepowertrain control module (PCM). The PCM willthen control the injection sequence and injector pulsewidth by turning the ground circuit to each individ-ual injector on and off. The PCM ignores the oxygensensor input signal and provides a predeterminedamount of additional fuel. This is done by adjustinginjector pulse width.• The PCM adjusts ignition timing by turning theground path to the coil on and off.• The PCM opens the ground circuit to the A/Cclutch relay to disengage the A/C compressor clutch.This will be done for approximately 15 seconds if theair conditioning system is operating.

If the vehicle has a manual transmission, the up-shift lamp is operated by the PCM.

IGNITION SWITCH OFF MODEWhen ignition switch is turned to the OFF posi-

tion, the PCM stops operating the injectors, ignitioncoil, ASD relay and fuel pump relay.

THROTTLE BODYFiltered air from the air cleaner enters the intake

manifold through the throttle body (Fig. 17). Fueldoes not enter the intake manifold through the throt-tle body. Fuel is sprayed into the manifold by the fuelinjectors. The throttle body is mounted on the intakemanifold. It contains an air control passage con-trolled by an idle air control (IAC) motor. The aircontrol passage is used to supply air for idle condi-tions. A throttle valve (plate) is used to supply air forabove idle conditions.

The throttle position sensor (TPS) and idle air con-trol (IAC) motor are attached to the throttle body.The accelerator pedal cable, speed control cable andtransmission control cable (when equipped) are con-nected to the throttle arm.


FUEL RAILThe fuel rail supplies fuel to the injectors and is

mounted to the intake manifold (Fig. 18). The fuelpressure regulator is no longer attached to the fuelrail. It is now part of the fuel pump module. The fuelpressure test port is integral with the rail and therail is not repairable.

FUEL PRESSURE REGULATORThe fuel pressure regulator is no longer attached to

the fuel rail. Refer to the Fuel Delivery section ofthis group for information.

Fig. 17 Throttle Body—Typical

Fig. 18 Fuel Rail—Typical


MULTI-PORT FUEL INJECTION (MFI)—4.0L 6 CYL. ENGINE—GENERALDIAGNOSIS

INDEX

page page

Automatic Shutdown (ASD) Relay Testing . . . . . . . 34Camshaft Position Sensor Test . . . . . . . . . . . . . . . 34Crankshaft Position Sensor Test . . . . . . . . . . . . . . 35Diagnostic Trouble Code (DTC) . . . . . . . . . . . . . . . 41DRB Scan Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Engine Coolant Temperature Sensor Test . . . . . . . 34Fuel Injector Test . . . . . . . . . . . . . . . . . . . . . . . . . 37Fuel Pump Relay Testing . . . . . . . . . . . . . . . . . . . 34Fuel System Pressure Test . . . . . . . . . . . . . . . . . . 38General Information . . . . . . . . . . . . . . . . . . . . . . . 29Idle Air Control Motor Test . . . . . . . . . . . . . . . . . . . 36Intake Manifold Air Temperature Sensor Test . . . . . 34

Manifold Absolute Pressure (MAP) Sensor Test . . . 35On-Board Diagnostics (OBD) . . . . . . . . . . . . . . . . . 38Oxygen Sensor (O2S) Heating Element Test . . . . . 36PCM System Schematics . . . . . . . . . . . . . . . . . . . 32Powertrain Control Module (PCM) 60-Way

Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32Relays—Operation/Testing . . . . . . . . . . . . . . . . . . 37Starter Motor Relay Test . . . . . . . . . . . . . . . . . . . . 37Throttle Position Sensor (TPS) Test . . . . . . . . . . . . 35Vehicle Speed Sensor Test . . . . . . . . . . . . . . . . . . 36Visual Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . 29

GENERAL INFORMATIONAll 4.0L engines are equipped with sequential


VISUAL INSPECTIONA visual inspection for loose, disconnected, or incor-

rectly routed wires and hoses should be made. Thisshould be done before attempting to diagnose or ser-vice the fuel injection system. A visual check willhelp spot these faults and save unnecessary test anddiagnostic time. A thorough visual inspection will in-clude the following checks:

(1) Verify that the 60-way connector is fully in-serted into the connector of the powertrain controlmodule (PCM) (Fig. 1). Verify that the connectormounting bolt is tightened to 4 Nzm (35 in. lbs.)torque.

(2) Inspect the battery cable connections. Be surethat they are clean and tight.

(3) Inspect fuel pump relay, air conditioning com-pressor clutch relay (if equipped) and ASD relay.These are located in the power distribution center(Fig. 2). Inspect starter motor relay connections. In-spect relays for signs of physical damage and corro-sion.

(4) Inspect ignition coil connections. Look for bentor spread pins in the connector. Verify that coil sec-ondary cable is firmly connected to coil (Fig. 3).

(5) Verify that distributor cap is correctly attachedto distributor. Be sure that spark plug cables arefirmly connected to the distributor cap and the sparkplugs are in their correct firing order. Be sure thatcoil cable is firmly connected to distributor cap andcoil. Be sure that camshaft position sensor wire con-nector (from in the distributor) is firmly connected to

main harness connector (Fig. 4). Inspect spark plugcondition. Refer to Group 8D, Ignition System. Con-nect vehicle to an oscilloscope and inspect sparkevents for fouled or damaged spark plugs or cables.

(6) Verify that generator output wire, generatorconnector and ground wire are firmly connected tothe generator (Fig. 5).

(7) Inspect the system ground connections. Refer toGroup 8, Wiring Diagrams for ground locations. Besure bolts are tight and ground terminals are clean.The powertrain control module (PCM) is grounded di-rectly, and plugged individually, to the negative bat-tery cable with a small jumper harness.

Fig. 1 Powertrain Control Module (PCM) Connector

ZJ FUEL SYSTEM GENERAL DIAGNOSIS—4.0L 6 CYL. ENGINE 14 - 29

(8) Verify that crankcase ventilation (CCV) freshair hose is firmly connected to cylinder head and aircleaner covers. Refer to Group 25, Emission ControlSystem for information.

(9) Inspect fuel line/tube quick-connect fitting-to-fuel rail connection (Fig. 6). For procedures, refer toFuel Tubes/Lines/Hoses and Clamps in this group.Also refer to Quick-Connect Fittings in this group.

(10) Verify that hose connections to all ports ofvacuum fittings on intake manifold are tight and notleaking.

(11) Inspect accelerator cable, transmission throttlecable (if equipped) and cruise control cable connec-tions (if equipped). Check their connections to thethrottle arm of throttle body for any binding or re-strictions (Fig. 7).

(12) Verify that brake vacuum booster hose isfirmly connected to fitting on intake manifold. Alsocheck connection to brake vacuum booster.

Fig. 2 Power Distribution Center

Fig. 3 Ignition Coil—Typical

Fig. 4 Cap, Plug Cables and Sensor Connector—Typical

Fig. 5 Generator Connector and Output WireConnections—Typical

Fig. 6 Fuel Supply Line—Typical

14 - 30 FUEL SYSTEM GENERAL DIAGNOSIS—4.0L 6 CYL. ENGINE ZJ

(13) Inspect the air cleaner inlet and air cleaner el-ement for restrictions.

(14) Inspect radiator grille area, radiator fins andair conditioning condenser for restrictions.

(15) Verify that intake manifold air temperaturesensor wire connector is firmly connected to harnessconnector (Fig. 8).

(16) Verify that MAP sensor electrical connector isfirmly connected to MAP sensor (Fig. 9). Verify thatvacuum hose is firmly connected to MAP sensor andto the intake manifold.

(17) Verify that fuel injector wire harness connec-tors are firmly connected to the fuel injectors in thecorrect firing order. Each harness connector is taggedwith the number of its corresponding fuel injector(Fig. 10).

(18) Verify that harness connectors are firmly con-nected to idle air control motor and throttle positionsensor.

(19) Verify that wire harness connector is firmlyconnected to the engine coolant temperature sensor(Fig. 11).

Fig. 7 Accelerator Cable, Throttle Cable and SpeedControl Cable

Fig. 8 Sensor Connectors

Fig. 9 Manifold Absolute Pressure (MAP) Sensor

Fig. 10 Fuel Injector Wire Harness—Typical

Fig. 11 Engine Coolant Temperature Sensor—Typical


(20) Verify that oxygen sensor wire connector isfirmly connected to the sensor. Inspect sensor andconnector for damage (Fig. 12).

(21) Raise and support the vehicle.(22) Inspect for pinched or leaking fuel lines/tubes.

Inspect for pinched cracked or leaking fuel lines. Re-fer to Fuel Tubes/Lines/Hoses and Clamps in thisgroup. Also refer to Quick-Connect Fittings in thisgroup.

(23) Inspect for exhaust system restrictions suchas pinched exhaust pipes, collapsed muffler orplugged catalytic convertor.

(24) If equipped with automatic transmission, ver-ify that electrical harness is firmly connected to neu-tral safety switch. Refer to the AutomaticTransmission section of Group 21.

(25) Verify that the harness connector is firmlyconnected to the vehicle speed sensor (Fig. 13).

(26) Verify that fuel pump/gauge sender unit wireconnector (located near front of fuel tank) is firmlyconnected to harness connector.

(27) Inspect fuel lines at front of fuel tank forcracks or leaks. Refer to Fuel Tubes/Lines/Hoses andClamps in this group. Also refer to Quick-ConnectFittings in this group.

(28) Inspect transmission torque convertor housing(automatic transmission) or clutch housing (manualtransmission) for damage to timing ring on driveplate/flywheel.

(29) Verify that battery cable and solenoid feedwire connections to the starter solenoid are tight andclean. Inspect for chaffed wires or wires rubbing upagainst other components (Fig. 14).

POWERTRAIN CONTROL MODULE (PCM) 60-WAYCONNECTOR

For PCM 60-way connector wiring schematics, referto Group 8W, Wiring Diagrams.

PCM SYSTEM SCHEMATICSA powertrain control system schematic for the fuel

injected 4.0L 6-cylinder engine is shown in figure 15.The schematic is displayed as a quick reference

only. It is not intended to be all-inclusive. Refer tothe Wiring Diagrams section for detailed information.

Fig. 12 Oxygen Sensor Location—Typical


Fig. 14 Starter Solenoid Connection—Typical


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AUTOMATIC SHUTDOWN (ASD) RELAY TESTINGTo perform a complete test of the ASD relay and its

circuitry, refer to the DRB scan tool and appropriatePowertrain Diagnostics Procedures manual. To testthe relay only, refer to Relays—Operation/Testing inthis section of the group.

CAMSHAFT POSITION SENSOR TESTRefer to Group 8D, Ignition Systems, for Camshaft

Position Sensor testing.

ENGINE COOLANT TEMPERATURE SENSOR TESTTo perform a complete test of this sensor and its

circuitry, refer to DRB scan tool and appropriatePowertrain Diagnostics Procedures manual. To testthe sensor only, refer to the following:

Disconnect wire harness connector from enginecoolant temperature sensor (Fig. 16).

Test the resistance of the sensor with a high inputimpedance (digital) volt-ohmmeter. The resistanceshould be less than 1000 ohms with the engine at itscorrect operating temperature. Refer to the CoolantTemperature Sensor/Manifold Air Temperature Sen-sor resistance chart. Replace the sensor if it is notwithin the range of resistance specified in the chart.

Test continuity of the wire harness. Do this be-tween the powertrain control module (PCM) wireharness connector terminal/pin-2 and the sensor con-nector terminal. Also test continuity of wire harnessterminal/pin-4 to the sensor connector terminal. Re-pair the wire harness if an open circuit is indicated.

FUEL PUMP RELAY TESTINGFor testing this relay, refer to Relays—Operation/

Testing in this section of the group.

INTAKE MANIFOLD AIR TEMPERATURE SENSORTEST

To perform a complete test of this sensor and itscircuitry, refer to DRB scan tool and appropriatePowertrain Diagnostics Procedures manual. To testthe sensor only, refer to the following:

Disconnect the wire harness connector from the in-take manifold air temperature sensor (Fig. 17).

Test the resistance of the sensor with an input im-pedance (digital) volt-ohmmeter. The resistanceshould be less than 4000 ohms with the engine at op-erating temperature. The longer the engine idles, thewarmer the intake manifold temperature will be-come. Refer to the Coolant Temperature Sensor/Man-

Fig. 16 Coolant Temperature Sensor—Typical

SENSOR RESISTANCE (OHMS)—COOLANTTEMPERATURE SENSOR/MANIFOLD AIR

TEMPERATURE

Fig. 17 Air Temperature Sensor


ifold Air Temperature Sensor resistance chart.Replace the sensor if it is not within the range of re-sistance specified in the chart.

Test the resistance of the wire harness. Do this be-tween the powertrain control module (PCM) wireharness connector terminal/pin-21 and the sensorconnector terminal. Also test terminal/pin-4 to thesensor connector terminal. Repair the wire harnessas necessary if the resistance is greater than 1 ohm.

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSORTEST


Inspect the MAP sensor vacuum hose connectionsat the throttle body and sensor. Repair as necessary.

CAUTION: When testing, do not remove the electri-cal connector from MAP sensor (Fig. 18). Be surethat the MAP sensor harness wires are not dam-aged by the test meter probes.

Test the MAP sensor output voltage at the MAPsensor connector between terminals-A and B (asmarked on the sensor body) (Fig. 19). With the igni-tion switch ON and the engine OFF, output voltageshould be 4-to-5 volts. The voltage should drop to 1.5-to-2.1 volts with a neutral-hot idle speed condition.

Test MAP sensor supply voltage at sensor connec-tor between terminals-A and C (Fig. 19) with the ig-nition ON and engine OFF. The voltage should beapproximately 5 volts (60.5V). Five volts (60.5V)should also be at terminal/pin-6 of the PCM wireharness connector. Repair or replace the wire harnessas necessary.

Test the MAP sensor ground circuit at sensor con-nector terminal-A (Fig. 19) and PCM connector termi-nal/pin-4. Repair the wire harness if necessary.

Test the MAP sensor ground circuit at the PCMconnector between terminal/pin-4 and terminal/pin-11 with an ohmmeter. If the ohmmeter indicatesan open circuit, inspect for a defective sensor groundconnection. Refer to Group 8W, Wiring for location ofengine grounds. If the ground connection is good, re-place the PCM. If terminal-4 has a short circuit to 12volts, correct this condition before replacing thePCM.

CRANKSHAFT POSITION SENSOR TESTRefer to Group 8D, Ignition Systems for test proce-

dures.

THROTTLE POSITION SENSOR (TPS) TESTTo perform a complete test of this sensor and its


The throttle position sensor (TPS) can be testedwith a digital voltmeter. The center terminal of theTPS is the output terminal (Fig. 20).

With the ignition key in the ON position, back-probe the TPS connector. Check the TPS output volt-age at the center terminal wire of the connector.Check this at idle (throttle plate closed) and at wideopen throttle (WOT). At idle, TPS output voltageshould must be greater than 200 millivolts. At wideopen throttle, TPS output voltage must be less than4.8 volts. The output voltage should increase gradu-ally as the throttle plate is slowly opened from idle toWOT.

Fig. 18 MAP Sensor Location

Fig. 19 MAP Sensor Connector Terminals—Typical


VEHICLE SPEED SENSOR TESTTo perform a complete test of the sensor and its cir-

cuitry, refer to DRB scan tool and appropriate Pow-ertrain Diagnostics Procedures manual.

OXYGEN SENSOR (O2S) HEATING ELEMENT TESTTo perform a complete test of this sensor and its


With the sensor at room temperature 25 degrees C(77 degrees F), disconnect the O2S sensor connector(Fig. 21). Connect the ohmmeter test leads across thewhite wire terminals of the sensor connector. Resis-tance should be between 5 and 7 ohms. Replace thesensor if the ohmmeter displays an infinity (open)reading.

IDLE AIR CONTROL MOTOR TESTTo perform a complete test of the idle air control

motor and its circuitry, refer to DRB scan tool and

appropriate Powertrain Diagnostics Procedures man-ual. To test the control motor only, refer to the follow-ing:

Idle air control motor operation can be tested usingspecial exerciser tool number 7558 (Fig. 22).

CAUTION: Proper safety precautions must be takenwhen testing the idle air control motor:

• Set the parking brake and block the drive wheels• Route all tester cables away from the cooling fans,drive belt, pulleys and exhaust components• Provide proper ventilation while operating the en-gine• Always return the engine idle speed to normal be-fore disconnecting the exerciser tool

(1) With the ignition OFF, disconnect the idle aircontrol motor wire connector at throttle body (Fig.22).

(2) Plug the exerciser tool number 7558 harnessconnector into the idle air control motor.

(3) Connect the red clip of exerciser tool 7558 tobattery positive terminal. Connect the black clip tonegative battery terminal. The red lamp on the exer-ciser tool will flash when the tool is properly con-nected.

(4) Start engine.When the switch on the tool is in the HIGH or

LOW position, the lamp on the tool will flash. Thisindicates that voltage pulses are being sent to theidle air control stepper motor.

(5) Move the switch to the HIGH position. The en-gine speed should increase. Move the switch to theLOW position. The engine speed should decrease.

(a) If the engine speed changes while using theexerciser tool, the idle air control motor is function-ing properly. Disconnect the exerciser tool and con-nect the idle air control motor wire connector to thestepper motor.

Fig. 20 Throttle Position Sensor (TPS) Testing—Typical

Fig. 21 Oxygen Sensor—Typical

Fig. 22 Idle Air Control Motor Testing


(b) If the engine speed does not change, turn theignition OFF and proceed to step (6). Do not dis-connect exerciser tool from the idle air control mo-tor.(6) Remove the idle air control motor from the

throttle body. Do not remove idle speed motor hous-ing from throttle body.

CAUTION: When checking idle air control motor op-eration with the motor removed from the throttlebody, do not extend the pintle (Fig. 23) more than6.35 mm (.250 in). If the pintle is extended morethan this amount, it may separate from the idle aircontrol motor. The idle air control motor must bereplaced if the pintle separates from the motor.

(7) With the ignition OFF, cycle the exerciser toolswitch between the HIGH and LOW positions. Ob-serve the pintle. The pintle should move in-and-outof the motor.

(a) If the pintle does not move, replace the idleair control motor. Start the engine and test the re-placement motor operation as described in step (5).

(b) If the pintle operates properly, check the idleair control motor bore in the throttle body bore forblockage and clean as necessary. Reinstall the idleair control motor and retest. If blockage is notfound, refer to the DRB scan tool and the appropri-ate Powertrain Diagnostics Procedures servicemanual.

RELAYS—OPERATION/TESTING

OPERATIONThe following operations/tests apply to these

relays only: Automatic shutdown (ASD) and fuelpump. For operations/tests on all other relays, referto the appropriate section of this service manual.

The relay terminal numbers from (Fig. 24) can befound on the bottom of the relay:

• Terminal number 30 is connected to battery volt-age and can be switched or B+ (hot) at all times.• Terminal number 87A is connected (a circuit isformed) to terminal 30 in the de-energized (normallyOFF) position.• Terminal number 87 is connected (a circuit isformed) to terminal 30 in the energized (ON) posi-tion. Terminal number 87 then supplies battery volt-age to the component being operated.• Terminal number 86 is connected to a switched (+)power source.• Terminal number 85 is grounded by the power-train control module (PCM).

TESTING(1) Remove relay before testing.(2) Using an ohmmeter, perform a resistance test

between terminals 85 and 86. Resistance value(ohms) should be 75 65 ohms for resistor equippedrelays.

(3) Connect the ohmmeter between terminals num-ber 87A and 30. Continuity should be present at thistime.

(4) Connect the ohmmeter between terminals num-ber 87 and 30. Continuity should not be present atthis time.

(5) Use a set of jumper wires (16 gauge or small-er). Connect one jumper wire between terminal num-ber 85 (on the relay) to the ground side (-) of a 12Volt power source.

(6) Attach the other jumper wire to the positiveside (+) of a 12V power source. Do not connect thejumper wire to relay at this time.

CAUTION: Do not allow the ohmmeter to contactterminals 85 or 86 during these tests. Damage toohmmeter may result.

(7) Attach the other jumper wire (12V +) to termi-nal number 86. This will activate the relay. Continu-ity should now be present between terminals number87 and 30. Continuity should not be present betweenterminals number 87A and 30.

(8) Disconnect jumper wires from relay and 12 Voltpower source.

If continuity or resistance tests did not pass, re-place relay. If tests passed, refer to Group 8W, WiringDiagrams for additional circuit information. Also re-fer to the Powertrain Diagnostic Procedures manualfor operation of the DRB scan tool.

STARTER MOTOR RELAY TESTRefer to Group 8A, Battery/Starting/Charging Sys-

tem Diagnostics, for starter motor relay testing.

FUEL INJECTOR TESTTo perform a complete test of the fuel injectors and

their circuitry, refer to DRB scan tool and appropri-

Fig. 23 Idle Air Control Motor Pintle


ate Powertrain Diagnostics Procedures manual. Totest the injector only, refer to the following:

Disconnect the injector wire connector from the in-jector. Place an ohmmeter on the injector terminals.Resistance reading should be approximately 14.5ohms 61.2 ohms at 20°C (68°F). Proceed to followingInjector Diagnosis chart. When performing the fol-lowing tests from the chart, do not leave elec-trical current applied to the injector for longerthan five seconds. Damage to injector coil or in-ternal injector seals could result.

FUEL SYSTEM PRESSURE TESTRefer to the Fuel Delivery System section of this

group.

ON-BOARD DIAGNOSTICS (OBD)The powertrain control module (PCM) has been

programmed to monitor many different circuits of thefuel injection system. If a problem is sensed in amonitored circuit often enough to indicate an actualproblem, a Diagnostic Trouble Code (DTC) is stored.The DTC will be stored in the PCM memory for even-tual display to the service technician. If the problemis repaired or ceases to exist, the PCM cancels theDTC after 51 engine starts.

Certain criteria must be met for a diagnostic trou-ble code (DTC) to be entered into PCM memory. Thecriteria may be a specific range of engine rpm, enginetemperature and/or input voltage to the PCM.

It is possible that a DTC for a monitored circuitmay not be entered into memory even though a mal-function has occurred. This may happen because oneof the DTC criteria for the circuit has not been met.Example: assume that one of the criteria for theMAP sensor circuit is that the engine must be oper-ating between 750 and 2000 rpm to be monitored fora DTC. If the MAP sensor output circuit shorts toground when the engine rpm is above 2400 rpm, a 0volt input will be seen by the PCM. A DTC will not

Fig. 24 Relay Terminals

Fig. 25 Fuel Injector Internal Components—Typical


INJECTOR DIAGNOSIS—VEHICLE RUNS ROUGH AND/OR HAS A MISS


be entered into memory because the condition doesnot occur within the specified rpm range.

A DTC indicates that the powertrain control mod-ule (PCM) has recognized an abnormal signal in acircuit or the system. A DTC may indicate the resultof a failure, but never identify the failed componentdirectly.

There are several operating conditions that thePCM does not monitor and set a DTC for. Refer tothe following Monitored Circuits and Non-MonitoredCircuits in this section.

MONITORED CIRCUITSThe powertrain control module (PCM) can detect

certain problems in the fuel injection system.Open or Shorted Circuit - The PCM can deter-

mine if sensor output (which is the input to PCM) iswithin proper range. It also determines if the circuitis open or shorted.

Output Device Current Flow - The PCM senseswhether the output devices are hooked up.

If there is a problem with the circuit, the PCMsenses whether the circuit is open, shorted to ground(-), or shorted to (+) voltage.

Oxygen Sensor - The PCM can determine if theoxygen sensor is switching between rich and lean.This is, once the system has entered Closed Loop. Re-fer to Open Loop/Closed Loop Modes Of Operation inthe Component Description/System Operation sectionfor an explanation of Closed (or Open) Loop opera-tion.

NON-MONITORED CIRCUITSThe PCM does not monitor the following circuits,

systems or conditions that could have malfunctionsthat result in driveability problems. A DiagnosticTrouble Code (DTC) may not be displayed for theseconditions.

Fuel Pressure: Fuel pressure is controlled by thefuel pressure regulator. The PCM cannot detect aclogged fuel pump inlet filter, clogged in-line fuel fil-ter, or a pinched fuel supply line. However, thesecould result in a rich or lean condition causing an ox-ygen sensor DTC to be stored in the PCM.

Secondary Ignition Circuit: The PCM cannotdetect an inoperative ignition coil, fouled or wornspark plugs, ignition cross firing, or open circuitedspark plug cables.

Engine Timing: The PCM cannot detect an incor-rectly indexed timing chain, camshaft sprocket orcrankshaft sprocket. The PCM also cannot detect anincorrectly indexed distributor. However, these couldresult in a rich or lean condition causing an oxygensensor DTC to be stored in the PCM.

Cylinder Compression: The PCM cannot detectuneven, low, or high engine cylinder compression.

Exhaust System: The PCM cannot detect aplugged, restricted or leaking exhaust system.

Fuel Injector Malfunctions: The PCM cannot de-termine if the fuel injector is clogged, or the wronginjector is installed. However, these could result in arich or lean condition causing an oxygen sensor DTCto be stored in the PCM.

Excessive Oil Consumption: Although the PCMmonitors exhaust stream oxygen content through ox-ygen sensor (closed loop), it cannot determine exces-sive oil consumption.

Throttle Body Air Flow: The PCM cannot detecta clogged or restricted air cleaner inlet or air cleanerelement.

Evaporative System: The PCM will not detect arestricted, plugged or loaded EVAP canister.

Vacuum Assist: Leaks or restrictions in the vac-uum circuits of vacuum assisted engine control sys-tem devices are not monitored by the PCM. However,a vacuum leak at the MAP sensor will be monitoredand a diagnostic trouble code (DTC) will be gener-ated by the PCM.

Powertrain Control Module (PCM) SystemGround: The PCM cannot determine a poor systemground. However, a DTC may be generated as a re-sult of this condition.

Powertrain Control Module (PCM) ConnectorEngagement: The PCM cannot determine spread ordamaged connector pins. However, a DTC may begenerated as a result of this condition.

HIGH AND LOW LIMITSThe powertrain control module (PCM) compares in-

put signal voltages from each input device. It will es-tablish high and low limits that are programmed intoit for that device. If the input voltage is not withinspecifications and other Diagnostic Trouble Code(DTC) criteria are met, a DTC will be stored in mem-ory. Other DTC criteria might include engine rpmlimits or input voltages from other sensors orswitches. The other inputs might have to be sensedby the PCM when it senses a high or low input volt-age from the control system device in question.

ACCESSING DIAGNOSTIC TROUBLE CODESA stored Diagnostic Trouble Code (DTC) can be dis-

played by cycling the ignition key On-Off-On-Off-Onwithin three seconds and observing the malfunctionindicator lamp. This lamp is displayed on the instru-ment panel as the CHECK ENGINE lamp (Fig. 26).

They can also be displayed through the use of theDiagnostic Readout Box (DRB scan tool). The DRBconnects to the data link connector in the vehicle(Fig. 27). For operation of the DRB, refer to the ap-propriate Powertrain Diagnostic Procedures servicemanual.

EXAMPLES:• If the lamp (Fig. 26) flashes 1 time, pauses andflashes 2 more times, a flashing Diagnostic Trouble


Code (DTC) number 12 is indicated. If this code isobserved, it is indicating that the battery has beendisconnected within the last 50 key-on cycles. Itcould also indicate that battery voltage has been dis-connected to the PCM. In either case, other DTC’smay have been erased.• If the lamp flashes 3 times, pauses and flashes 1more time, a Diagnostic Trouble Code (DTC) number31 is indicated.

• If the lamp flashes 1 time, pauses and flashes 4more times, a Diagnostic Trouble Code (DTC) num-ber 14 is indicated.

After any stored DTC information has been ob-served, the display will end with a flashing DTCnumber 55. This will indicate the end of all stored in-formation.

Refer to the Diagnostic Trouble Code (DTC) chartsfor DTC identification.

If the problem is repaired or ceases to exist, thepowertrain control module (PCM) cancels the DTCafter 51 engine starts.

Diagnostic Trouble Codes indicate the results of afailure, but never identify the failed component di-rectly.

The circuits of the data link connector are shown in(Fig. 28).

ERASING TROUBLE CODESUse the DRB scan tool to erase a Diagnostic Trou-

ble Code (DTC). Refer to the appropriate PowertrainDiagnostic Procedures service manual for operationof the DRB scan tool.

DRB SCAN TOOLFor operation of the DRB scan tool, refer to the ap-

propriate Powertrain Diagnostic Procedures servicemanual.

DIAGNOSTIC TROUBLE CODE (DTC)On the following pages, a list of diagnostic trouble

codes is provided for the 4.0L 6-cylinder engine. ADTC indicates that the powertrain control module(PCM) has recognized an abnormal signal in a circuitor the system. A DTC may indicate the result of afailure, but never identify the failed component di-rectly.



Fig. 28 Data Link Connector Schematic


DIAGNOSTIC TROUBLE CODE DESCRIPTIONSDiagnostic

Trouble CodeDRB Scan Tool Display Description of Diagnostic Trouble Code

11* No Crank Reference Signal at PCM No crank reference signal detected during en-gine cranking.

12* Battery Disconnect Direct battery input to PCM was disconnectedwithin the last 50 Key-on cycles.

13** No Change in MAP From Start to Run No difference recognized between the engineMAP reading and the barometric (atmospheric)pressure reading at start-up.

14** MAP Sensor Voltage Too Low MAP sensor input below minimum acceptablevoltage.

or

MAP Sensor Voltage Too High MAP sensor input above maximum acceptablevoltage.

15** No Vehicle Speed Sensor Signal No vehicle distance (speed) sensor signal de-tected during road load conditions.

17* Engine is Cold Too Long Engine coolant temperature remains belownormal operating temperatures during vehicletravel (thermostat).

21** O2S Stays at Center Neither rich or lean condition detected fromthe oxygen sensor input.

or

O2S Shorted to Voltage Oxygen sensor input voltage maintained abovethe normal operating range.

22** ECT Sensor Voltage Too High Engine coolant temperature sensor inputabove maximum acceptable voltage.

or

ECT Sensor Voltage Too Low Engine coolant temperature sensor input belowminimum acceptable voltage.

23** Intake Air Temp Sensor Voltage Low Intake manifold air temperature sensor inputbelow the minimum acceptable voltage.

or

Intake Air Temp Sensor Voltage High Intake manifold air temperature sensor inputabove the maximum acceptable voltage.

24** Throttle Position Sensor Voltage High Throttle position sensor input above the maxi-mum acceptable voltage.

or

Throttle Position Sensor Voltage Low Throttle position sensor input below the mini-mum acceptable voltage.

* Check Engine Lamp will not illuminate at all times if this Diagnostic Trouble Code was recorded. CycleIgnition key as described in manual and observe code flashed by Check Engine lamp.

** Check Engine Lamp will illuminate during engine operation if this Diagnostic Trouble Code was recorded.


DIAGNOSTIC TROUBLE CODE DESCRIPTIONS—CONTINEUDDiagnostic


25** Idle Air Control Motor Circuits A shorted condition detected in one or more ofthe idle air control motor circuits.

27* Injector #1 Control Circuit Injector #1 output driver does not respondproperly to the control signal.

or

Injector #2 Control Circuit Injector #2 output driver does not respondproperly to the control signal.

or


or


or


or


31** EVAP Solenoid Circuit An open or shorted condition detected in theEVAP solenoid circuit. This code is used forthe 4.0L engine when equipped with the Cali-fornia Emission Package only.

33* A/C Clutch Relay Circuit An open or shorted condition detected in theA/C clutch relay circuit.

34* Speed Control Solenoid Circuits An open or shorted condition detected in theSpeed Control vacuum or vent solenoid cir-cuits.

or

Speed Control Switch Always Low Speed Control switch input below the mini-mum acceptable voltage.

or

Speed Control Switch Always High Speed Control switch input above the maxi-mum acceptable voltage.

41** Generator Field Not Switching Properly An open or shorted condition detected in thegenerator field control circuit.




DIAGNOSTIC TROUBLE CODE DESCRIPTIONS—CONTINEUDDiagnostic


42* Auto Shutdown Relay Control Circuit An open or shorted condition detected in theauto shutdown relay circuit.

44* Battery Temp Sensor Volts out of Limit An open or shorted condition exists in the en-gine coolant temperature sensor circuit or aproblem exists in the PCM’s battery tempera-ture voltage circuit.

46** Charging System Voltage Too High Battery voltage sense input above targetcharging voltage during engine operation.

47** Charging System Voltage Too Low Battery voltage sense input below targetcharging during engine operation. Also, no sig-nificant change detected in battery voltageduring active test of generator output.

51** O2S Signal Stays Below Center (Lean) Oxygen sensor signal input indicates lean air/fuel ratio condition during engine operation.

52** O2S Signal Stays Above Center (Rich) Oxygen sensor signal input indicates rich air/fuel ratio condition during engine operation.

53* Internal PCM Failure PCM Internal fault condition detected.

or

PCM Failure SPI (Serial Peripheral Inter-face) Communications

PCM Internal fault condition detected.

54* No Cam Sync Signal at PCM No fuel sync (camshaft signal) detected duringengine cranking.

55* Display not shown on DRB scan tool Completion of diagnostic trouble code displayon the Malfunction Indicator Lamp (Check En-gine Lamp).

62* PCM Failure SRI miles not stored Unsuccessful attempt to update SRI (servicereminder indicator) miles in the PCM EE-PROM.

63* PCM Failure EEPROM Write Denied Unsuccessful attempt to write to an EEPROMlocation by the PCM.




MULTI-PORT FUEL INJECTION (MFI)—4.0L 6 CYL. ENGINE—COMPONENTREMOVAL/INSTALLATION

INDEX

page page

Accelerator Pedal and Throttle Cable . . . . . . . . . . . 46Air Cleaner Element . . . . . . . . . . . . . . . . . . . . . . . 45Air Cleaner Housing . . . . . . . . . . . . . . . . . . . . . . . 45Air Conditioning (A/C) Clutch Relay . . . . . . . . . . . . 46Automatic Shutdown (ASD) Relay . . . . . . . . . . . . . 46Brake Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46Camshaft Position Sensor . . . . . . . . . . . . . . . . . . . 46Crankshaft Position Sensor . . . . . . . . . . . . . . . . . . 47Engine Coolant Temperature Sensor . . . . . . . . . . . 47Fuel Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Fuel Injector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Fuel Pressure Regulator . . . . . . . . . . . . . . . . . . . . 48Fuel Pump Module . . . . . . . . . . . . . . . . . . . . . . . . 48Fuel Pump Relay . . . . . . . . . . . . . . . . . . . . . . . . . 48Fuel Rail Assembly . . . . . . . . . . . . . . . . . . . . . . . . 48Fuel System Pressure Release Procedure . . . . . . . 48

Fuel Tank Pressure Relief/Rollover Valve . . . . . . . . 49Fuel Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Fuel Tubes/Lines/Hoses and Clamps . . . . . . . . . . . 49Idle Air Control (IAC) Motor . . . . . . . . . . . . . . . . . . 49Ignition Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Intake Manifold . . . . . . . . . . . . . . . . . . . . . . . . . . . 49Intake Manifold Air Temperature Sensor . . . . . . . . . 46Manifold Absolute Pressure (MAP) Sensor . . . . . . . 49Oxygen (O2S) Sensor . . . . . . . . . . . . . . . . . . . . . . 49Park/Neutral Switch . . . . . . . . . . . . . . . . . . . . . . . . 50Powertrain Control Module (PCM) . . . . . . . . . . . . . 50Quick-Connect Fittings . . . . . . . . . . . . . . . . . . . . . 51Throttle Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51Throttle Position Sensor (TPS) . . . . . . . . . . . . . . . 51Vehicle Speed Sensor . . . . . . . . . . . . . . . . . . . . . . 52

AIR CLEANER HOUSING

REMOVAL(1) Unlock clean air hose clamp (Fig. 1) at air

cleaner cover. To unlock the clamp, attach adjustablepliers to clamp and rotate pliers as shown in figure 2.Remove clean air hose at cover.

(2) Remove crankcase breather/filter hose at aircleaner cover.

(3) From under vehicle, remove three housing nuts(Fig. 1).

(4) Release the air cleaner housing from the ambi-ent air duct and remove housing from vehicle.

INSTALLATION(1) Position air cleaner housing to body and ambi-

ent air duct (Fig. 1).(2) Install three nuts and tighten to 10 Nzm (93 in.

lbs.) torque.(3) Install crankcase breather/filter hose to cover.(4) Install clamp to cover. Compress the clamp

snugly with adjustable pliers as shown in figure 3.

AIR CLEANER ELEMENT

REMOVAL/INSTALLATION(1) Pry back the six clips retaining the air cleaner

cover to the air cleaner housing (Fig. 4).

Fig. 1 Air Cleaner—4.0L 6-Cylinder Engine—Typical

Fig. 2 Clamp Removal

ZJ FUEL SYSTEM COMPONENT REMOVAL/INSTALLATION—4.0L 6 CYL. ENGINE 14 - 45

(2) Lift the cover up and position to the side.(3) Remove air cleaner element.(4) Clean the inside of air cleaner housing before

installing new element.(5) Reverse the preceding operation for installa-

tion. Be sure the air cleaner cover is properly seatedto air cleaner housing.

ACCELERATOR PEDAL AND THROTTLE CABLERefer to the Accelerator Pedal and Throttle Cable

section of this group for removal/installation proce-dures.

AIR CONDITIONING (A/C) CLUTCH RELAYThe A/C clutch relay is located in the power distri-

bution center (PDC) (Fig. 5). For location of this relaywithin the PDC, refer to label attached to bottom ofPDC cover.

AUTOMATIC SHUTDOWN (ASD) RELAYThe ASD relay is located in the power distribution

center (Fig. 5) (PDC). For location of this relaywithin the PDC, refer to label attached to bottom ofPDC cover.

BRAKE SWITCHRefer to Group 5, Brakes for removal/installation

procedures.

CAMSHAFT POSITION SENSORFor removal/installation procedures, refer to Group

8D, Ignition System. See Camshaft Position Sensor.

INTAKE MANIFOLD AIR TEMPERATURE SENSORThe intake manifold air temperature sensor is in-

stalled into the intake manifold plenum (Fig. 6).

REMOVAL(1) Disconnect the electrical connector from the

sensor.(2) Remove the sensor from the intake manifold.

INSTALLATION(1) Install the sensor into the intake manifold.

Tighten the sensor to 28 Nzm (20 ft. lbs.) torque.(2) Connect the electrical connector to the sensor.

Fig. 3 Clamp Installation

Fig. 4 Typical Air Cleaner Element Removal/Installation


14 - 46 FUEL SYSTEM COMPONENT REMOVAL/INSTALLATION—4.0L 6 CYL. ENGINE ZJ

CRANKSHAFT POSITION SENSORRefer to Group 8D, Ignition Systems for proce-

dures.

ENGINE COOLANT TEMPERATURE SENSORThe coolant temperature sensor is installed in the

thermostat housing (Fig. 7).

REMOVAL(1) Drain cooling system until the coolant level is

below the cylinder head. Observe the WARNINGS inGroup 7, Cooling.

(2) Disconnect the coolant temperature sensor wireconnector.

(3) Remove the sensor from the thermostat hous-ing (Fig. 7).

INSTALLATION(1) Install coolant temperature sensor into the cyl-

inder block. Tighten to 28 Nzm (21 ft. lbs.) torque.(2) Connect the wire connector.(3) Fill the cooling system.

FUEL FILTERRefer to the Fuel Delivery System section of this

group for removal/installation procedures.

FUEL INJECTOR

REMOVAL(1) Remove the fuel rail. Refer to Fuel Rail Re-

moval in this section.(2) Remove the clip(s) that retain the fuel injec-

tor(s) to the fuel rail (Figs. 8 or 9).

INSTALLATION(1) Install the fuel injector(s) into the fuel rail as-

sembly and install retaining clip(s).(2) Install fuel rail. Refer to Fuel Rail Installation

in this section.(3) Start engine and check for fuel leaks.

Fig. 6 Sensor Location


Fig. 8 Injector Mounting

Fig. 9 Injector Retaining Clips


FUEL PRESSURE REGULATORThe fuel pressure regulator is part of the fuel

pump module and is not serviced separately. If itneeds replacement, the fuel pump module assemblymust be replaced. Refer to the Fuel Delivery sectionof this group for procedures.

FUEL PUMP MODULERefer to the Fuel Delivery System section of this


FUEL PUMP RELAYThe fuel pump relay is located in the power distri-

bution center (PDC) (Fig. 10). For location of this re-lay within the PDC, refer to label attached to bottomof PDC cover.

FUEL RAIL ASSEMBLY

REMOVAL

WARNING: THE FUEL SYSTEM IS UNDER CON-STANT FUEL PRESSURE EVEN WITH THE ENGINEOFF. THIS PRESSURE MUST BE RELEASED BE-FORE SERVICING THE FUEL RAIL.

(1) Remove fuel tank filler tube cap.(2) Disconnect the negative battery cable from bat-

tery.(3) Perform the Fuel System Pressure Release Pro-

cedure as described in the Fuel Delivery System sec-tion of this group.

(4) Remove and numerically attach a tag (if fuelinjector is not already tagged), the injector harnessconnectors. Do this at each injector (Fig. 11).

(5) Disconnect fuel supply line from fuel rail (Fig.11). Refer to Fuel Tubes/Lines/Hoses and Clamps, orQuick-Connect Fittings. These can both be found inthe Fuel Delivery section of this group.

(6) Remove fuel rail mounting bolts.On models with automatic transmissions, it may be

necessary to remove automatic transmission throttleline pressure cable and bracket. This will aid in fuelrail assembly removal.

(7) Remove fuel rail by gently rocking until all thefuel injectors are out of the intake manifold.

INSTALLATION(1) Position tips of all fuel injectors into the corre-

sponding injector bore in the intake manifold. Seatinjectors into manifold.

(2) Tighten fuel rail mounting bolts to 27 Nzm (20ft. lbs.) torque.

(3) Connect injector harness connectors to appro-priate (tagged) injector.

(4) Connect fuel supply line to fuel rail. Refer toFuel Tubes/Lines/Hoses and Clamps, or Quick-Con-nect Fittings. These can both be found in the FuelDelivery section of this group.

(5) Install protective cap to pressure test port fit-ting.

(6) Install fuel tank cap.(7) Connect negative battery cable to battery.(8) Start engine and check for fuel leaks.


WARNING: THE FUEL SYSTEM IS UNDER A CON-STANT PRESSURE EVEN WITH THE ENGINE OFF.BEFORE SERVICING THE FUEL PUMP, FUEL LINES,FUEL FILTER OR FUEL INJECTOR, THE FUEL SYS-TEM PRESSURE MUST BE RELEASED.

Refer to the Fuel Delivery System section of thisgroup. See Fuel System Pressure Release procedure.


Fig. 11 Fuel Injector Harness—Typical


FUEL TANKSRefer to the Fuel Tank section of this group for re-

moval/installation procedures.

FUEL TANK PRESSURE RELIEF/ROLLOVER VALVERefer to the Fuel Tank section of this group for re-


FUEL TUBES/LINES/HOSES AND CLAMPSRefer to Fuel Tubes/Lines/Hoses and Clamps in the

Fuel Delivery System section of this group for remov-al/installation procedures. Also refer to Quick-Con-nect Fittings in the Fuel Delivery section of thisgroup.

IDLE AIR CONTROL (IAC) MOTORThe idle air control motor is mounted to the throt-

tle body adjacent to the throttle position sensor (Fig.12).

REMOVAL(1) Disconnect the electrical connector from the

idle air control motor.

(2) Remove idle air control motor torx head mount-ing bolts.

(3) Remove idle air control motor.

INSTALLATION(1) Install idle air control motor into throttle body

and tighten retaining bolts.(2) Connect electrical connector to idle air control

motor.

IGNITION COILRefer to Group 8D, Ignition Systems for removal/

installation procedures.

INTAKE MANIFOLDRefer to Group 11, Exhaust System and Intake

Manifold for removal/installation procedures.

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSORThe MAP sensor is located on the dash panel near

the rear of the engine cylinder head cover (Fig. 13).

REMOVAL(1) Disconnect the MAP sensor electrical connector

(Fig. 13).(2) Disconnect the MAP sensor vacuum supply

hose (Fig. 13).(3) Remove the MAP sensor mounting bolts and re-

move MAP sensor.

INSTALLATION(1) Install MAP sensor to dash panel and secure

with mounting bolts.(2) Install the MAP sensor vacuum supply hose.(3) Connect the MAP sensor electrical connector.

OXYGEN (O2S) SENSORThe O2S sensor is installed in the exhaust down

pipe just below the exhaust manifold flange (Fig. 14).

Fig. 12 Idle Air Control Motor—Removal/Installation

Fig. 13 MAP Sensor



REMOVAL

WARNING: THE EXHAUST MANIFOLD BECOMESVERY HOT DURING ENGINE OPERATION. ALLOWENGINE TO COOL BEFORE REMOVING OXYGENSENSOR.

(1) Raise and support the vehicle.(2) The sensors electrical connector clip is pushed

over an oil pan mounting stud. Pull the connectorclip from the mounting stud.

(3) Separate the electrical connectors.(4) Remove the O2S sensor from the exhaust man-

ifold. Snap-On oxygen sensor wrench (number YA8875) may be used for removal and installation.

INSTALLATIONThreads of new factory oxygen sensors are coated

with anti-seize compound to aid in removal.(1) Install the O2S sensor into the exhaust mani-

fold and tighten to 30 Nzm (22 ft. lbs.) torque.(2) Connect the O2S sensor wire connector to the

main harness.(3) Push the sensor clip on firmly at the oil pan

stud.(4) Lower the vehicle.

PARK/NEUTRAL SWITCHRefer to Group 21, Transmissions for park/neutral

switch service.

POWERTRAIN CONTROL MODULE (PCM)The PCM is located on the cowl panel in the right/

rear side of the engine compartment (Fig. 15).

REMOVAL(1) Disconnect the negative battery cable at the

battery.(2) Remove the coolant reserve/overflow tank (one

bolt and two nuts) (Fig. 16)

(3) Loosen the 60-Way connector mounting bolt(Fig. 17).

(4) Remove the electrical connector by pullingstraight back.

(5) Remove the three PCM mounting bolts (Fig.17).

(6) Remove PCM.Fig. 15 Powertrain Control Module (PCM) Location

Fig. 16 Coolant Reserve/Overflow Tank Mounting

Fig. 17 Powertrain Control Module (PCM) Mounting


INSTALLATION(1) Check the pins in 60-way electrical connector

for damage. Repair as necessary.(2) Install PCM. Tighten three mounting bolts to 1

Nzm (9 in. lbs.) torque.(3) Engage 60-way connector into PCM. Tighten

connector mounting bolt to 4 Nzm (35 in. lbs.) torque.(4) Install coolant reserve/overflow tank.(5) Connect negative cable to battery.

QUICK-CONNECT FITTINGSRefer to the Fuel Delivery System section of this


THROTTLE BODY

REMOVAL(1) Disconnect the negative battery cable.(2) Disconnect air cleaner hose from throttle body.(3) Disconnect idle air control motor and throttle

position sensor wire connectors.(4) Disconnect accelerator cable, throttle cable (au-

tomatic transmission) and speed control cable (ifequipped) from throttle arm (Fig. 18).

(5) Remove throttle body mounting bolts, throttlebody and gasket. Discard old gasket (Fig. 19).

INSTALLATION(1) Install throttle body and new gasket. Tighten

throttle body mounting bolts to 12 Nzm (9 ft. lbs.)torque.

(2) Connect idle air control motor and throttle po-sition sensor wire connectors.

(3) Connect throttle linkage to throttle arm.

CAUTION: When the automatic transmission throttlecable is connected, it MUST be adjusted.

(4) If equipped with an automatic transmission,connect and adjust the transmission line pressure ca-ble. Refer to Group 21, Transmissions for adjustmentprocedure.

(5) Install air cleaner hose to throttle body.(6) Connect negative battery cable to battery.

THROTTLE POSITION SENSOR (TPS)

REMOVAL(1) Disconnect TPS electrical connector.(2) Remove TPS mounting bolts.(3) Remove TPS.

INSTALLATIONThe throttle shaft end of the throttle body slides

into a socket in the TPS (Fig. 20). The TPS must beinstalled so that it can be rotated a few degrees. Ifthe sensor will not rotate, install the sensor with thethrottle shaft on the other side of the socket tangs.The TPS will be under slight tension when rotated.

(1) Install the TPS and retaining bolts.

Fig. 18 Accelerator, Throttle and Speed ControlCables

Fig. 19 Throttle Body—Removal/Installation

Fig. 20 Throttle Position Sensor—Installation


(2) Connect TPS electrical connector to TPS.(3) Manually operate the throttle (by hand) to

check for any TPS binding before starting the engine.

VEHICLE SPEED SENSORThe vehicle speed sensor (Fig. 21) is located on the

extension housing of the transmission on 2WD mod-els. It is located on the transfer case on 4WD models.

REMOVAL

(1) Raise and support vehicle.(2) Clean the area around the sensor before re-

moval.

(3) Disconnect the electrical connector from thesensor.

(4) Remove the sensor mounting nut (Fig. 22).(5) Pull the sensor from the speedometer pinion

gear adapter for removal.

INSTALLATION(1) Install new sensor into speedometer gear

adapter.(2) Install and tighten sensor mounting bolt. To

prevent damage to sensor or speedometeradapter, be sure the sensor is mounted flush tothe adapter before tightening.

(3) Connect electrical connector to sensor.

Fig. 21 Vehicle Speed Sensor Location—Typical

Fig. 22 Sensor Removal/Installation—Typical


MULTI-PORT FUEL INJECTION (MFI)—5.2L V-8 ENGINE—COMPONENTDESCRIPTION/SYSTEM OPERATION

INDEX

page page

Air Conditioning (A/C) Clutch Relay—PCM Output . 59Air Conditioning (A/C) Controls—PCM Input . . . . . . 55Auto Shutdown (ASD) Relay—PCM Output . . . . . . 60Automatic Shutdown (ASD) Sense—PCM Input . . . 55Battery Voltage—PCM Input . . . . . . . . . . . . . . . . . 55Brake Switch—PCM Input . . . . . . . . . . . . . . . . . . . 55Camshaft Position Sensor—PCM Input . . . . . . . . . 55Crankshaft Position Sensor—PCM Input . . . . . . . . 56Data Link Connector—PCM Input . . . . . . . . . . . . . 55Data Link Connector—PCM Output . . . . . . . . . . . . 60EGR (Exhaust Gas Recirculation) Valve Control

Solenoid—PCM Output . . . . . . . . . . . . . . . . . . . 60Engine Coolant Temperature Sensor—PCM Input . 56EVAP Canister Purge Solenoid—PCM Output . . . . 60Fuel Injectors—PCM Output . . . . . . . . . . . . . . . . . 60Fuel Pressure Regulator . . . . . . . . . . . . . . . . . . . . 65Fuel Rail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64General Information . . . . . . . . . . . . . . . . . . . . . . . 53Generator Field—PCM Output . . . . . . . . . . . . . . . . 60Generator Lamp—PCM Output . . . . . . . . . . . . . . . 60Idle Air Control (IAC) Motor—PCM Output . . . . . . . 59Ignition Circuit Sense—PCM Input . . . . . . . . . . . . . 56

Ignition Coil—PCM Output . . . . . . . . . . . . . . . . . . . 61Intake Manifold Air Temperature Sensor—PCM

Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56Malfunction Indicator Lamp—PCM Output . . . . . . . 60Manifold Absolute Pressure (MAP) Sensor—PCM

Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57Open Loop/Closed Loop Modes of Operation . . . . . 61Overdrive/Override Switch . . . . . . . . . . . . . . . . . . . 57Oxygen (O2S) Sensor—PCM Input . . . . . . . . . . . . 57Park/Neutral Switch—PCM Input . . . . . . . . . . . . . . 58Power Ground . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Powertrain Control Module (PCM) . . . . . . . . . . . . . 54SCI Receive—PCM Input . . . . . . . . . . . . . . . . . . . 58SCI Transmit—PCM Output . . . . . . . . . . . . . . . . . . 61Sensor Return—PCM Input . . . . . . . . . . . . . . . . . . 58Shift Indicator—PCM Output . . . . . . . . . . . . . . . . . 61Speed Control—PCM Input . . . . . . . . . . . . . . . . . . 58Speed Control—PCM Output . . . . . . . . . . . . . . . . . 61Tachometer—PCM Output . . . . . . . . . . . . . . . . . . . 61Throttle Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64Throttle Position Sensor (TPS)—PCM Input . . . . . . 58Vehicle Speed Sensor—PCM Input . . . . . . . . . . . . 58

GENERAL INFORMATIONAll 5.2L V-8 engines are equipped with sequential


The powertrain control module (PCM) operates thefuel system. The PCM was formerly referred to asthe SBEC or engine controller. The PCM is a pre-pro-grammed, dual microprocessor digital computer. Itregulates ignition timing, air-fuel ratio, emission con-trol devices, charging system, speed control, air con-ditioning compressor clutch engagement and idlespeed. The PCM can adapt its programming to meetchanging operating conditions.

Powertrain Control Module (PCM) Inputs rep-resent the instantaneous engine operating conditions.Air-fuel mixture and ignition timing calibrations forvarious driving and atmospheric conditions are pre-programmed into the PCM. The PCM monitors andanalyzes various inputs. It then computes engine fueland ignition timing requirements based on these in-puts. Fuel delivery control and ignition timing willthen be adjusted accordingly.

Other inputs to the PCM are provided by the brakelight switch, air conditioning select switch and thespeed control switches. All inputs to the PCM areconverted into signals.

Electrically operated fuel injectors spray fuel inprecise metered amounts into the intake port directly

above the intake valve. The injectors are fired in aspecific sequence by the PCM. The PCM maintainsan air/fuel ratio of 14.7 to 1 by constantly adjustinginjector pulse width. Injector pulse width is thelength of time that the injector opens and sprays fuelinto the chamber. The PCM adjusts injector pulsewidth by opening and closing the ground path to theinjector.

Manifold absolute pressure (air density) and enginerpm (speed) are the primary inputs that determinefuel injector pulse width. The PCM also monitorsother inputs when adjusting air-fuel ratio.

Inputs That Effect Fuel Injector Pulse Width:• Exhaust gas oxygen content• Engine coolant temperature• Manifold absolute pressure (MAP)• Engine speed• Throttle position• Battery voltage• Air conditioning selection• Transmission gear selection (automatic transmis-sions only)• Speed control

The powertrain control module (PCM) adjusts igni-tion timing by controlling ignition coil operation. Theignition coil receives battery voltage when the igni-tion key is in the run or starter position. The PCMprovides a ground for the ignition coil. The coil dis-

ZJ FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—5.2L V-8 ENGINE 14 - 53

charges when the PCM supplies a ground. By switch-ing the ground path on and off, the PCM regulatesignition timing.

The sensors and switches that provide inputs tothe powertrain control module (PCM) comprise theEngine Control System. It is also comprised of thePCM Outputs (engine control devices that the are op-erated by the PCM).

SYSTEM DIAGNOSISThe powertrain control module (PCM) tests many

of its own input and output circuits. If a DiagnosticTrouble Code (DTC) is found in a major system, thisinformation is stored in the PCM memory. Refer toOn-Board Diagnostics in the Multi-Port Fuel Injec-tion—General Diagnosis—5.2L Engine section of thisgroup for DTC information.

POWERTRAIN CONTROL MODULE (PCM)The powertrain control module (PCM) (Fig. 1) oper-

ates the fuel system. The PCM was formerly referredto as the SBEC or engine controller. The PCM is apre-programmed, dual microprocessor digital com-puter. It regulates ignition timing, air-fuel ratio,emission control devices, charging system, speed con-trol, air conditioning compressor clutch engagementand idle speed. The PCM can adapt its programmingto meet changing operating conditions.

The PCM receives input signals from variousswitches and sensors. Based on these inputs, thePCM regulates various engine and vehicle operationsthrough different system components. These compo-nents are referred to as Powertrain Control Module(PCM) Outputs. The sensors and switches that pro-vide inputs to the PCM are considered PowertrainControl Module (PCM) Inputs.

The PCM adjusts ignition timing based upon in-puts it receives from sensors that react to: enginerpm, manifold absolute pressure, engine coolant tem-perature, throttle position, transmission gear selec-tion (automatic transmission), vehicle speed and thebrake switch.

The PCM adjusts idle speed based on inputs it re-ceives from sensors that react to: throttle position,vehicle speed, transmission gear selection, enginecoolant temperature and from inputs it receives fromthe air conditioning clutch switch and brake switch.

Based on inputs that it receives, the PCM adjustsignition coil dwell. The PCM also adjusts the gener-ator charge rate through control of the generatorfield and provides speed control operation.

Powertrain Control Module (PCM) Inputs:• Generator output• A/C request (if equipped with factory A/C)• A/C select (if equipped with factory A/C)• Auto shutdown (ASD) sense• Intake manifold air temperature sensor• Battery voltage

• Brake switch• Engine coolant temperature sensor• Crankshaft position sensor• Ignition circuit sense (ignition switch in run posi-tion)• Manifold absolute pressure sensor• Overdrive/override switch• Oxygen sensor• Park/neutral switch (auto. trans. only)• SCI receive (DRB scan tool connection)• Speed control resume switch• Speed control set switch• Speed control on/off switch• Camshaft position sensor signal• Throttle position sensor• Vehicle speed sensor• Sensor return• Power ground• Signal ground

Powertrain Control Module (PCM) Outputs:• A/C clutch relay• Idle air control (IAC) motor• Auto shutdown (ASD) relay• Generator field• Malfunction indicator lamp (Check engine lamp)• EGR valve control solenoid• Fuel injectors• Fuel pump relay• Ignition coil• EVAP canister purge solenoid• SCI transmit (DRB scan tool connection)• Shift indicator lamp (manual transmission only)• Speed control vacuum solenoid• Speed control vent solenoid

Fig. 1 Powertrain Control Module (PCM) Location

14 - 54 FUEL SYSTEM COMPONENT DESCRIPTION/SYSTEM OPERATION—5.2L V-8 ENGINE ZJ

• Tachometer (on instrument panel, if equipped)The powertrain control module (PCM) contains a

voltage convertor. This converts battery voltage to aregulated 8.0 volts. It is used to power the crankshaftposition sensor, camshaft position sensor and vehiclespeed sensor. The PCM also provides a five (5) voltsupply for the manifold absolute pressure (MAP) sen-sor and throttle position sensor (TPS).

AIR CONDITIONING (A/C) CONTROLS—PCM INPUTThe A/C control system information applies to fac-

tory installed air conditioning units.A/C SELECT SIGNAL: When the A/C switch is in

the ON position and the A/C low-pressure switch isclosed, an input signal is sent to the powertrain con-trol module (PCM). The signal informs the PCM thatthe A/C has been selected. The PCM then adjusts idlespeed to a pre-programmed rpm through the idle aircontrol (IAC) motor to compensate for increased en-gine load.

A/C REQUEST SIGNAL: Once A/C has been se-lected, the powertrain control module (PCM) receivesthe A/C request signal from the evaporator switch.The input indicates that the evaporator temperatureis in the proper range for A/C application. The PCMuses this input to cycle the A/C compressor clutchthrough the A/C relay. It will also determine the cor-rect engine idle speed through the idle air control(IAC) motor position.

If the A/C low-pressure switch opens, indicating alow refrigerant level, the PCM will not receive anA/C select signal. The PCM will then remove theground from the A/C relay. This will deactivate theA/C compressor clutch.

If the evaporator switch opens, (indicating thatevaporator is not in proper temperature range), thePCM will not receive the A/C request signal. ThePCM will then remove the ground from the A/C relay,deactivating the A/C compressor clutch.

AUTOMATIC SHUTDOWN (ASD) SENSE—PCMINPUT

A 12 volt signal at this input indicates to the PCMthat the ASD has been activated. The ASD relay islocated in the power distribution center (PDC) in theengine compartment. It is used to connect the oxygensensor heater element, ignition coil, generator fieldwinding and fuel injectors to 12 volt + power supply.

This input is used only to sense that the ASD relayis energized. If the powertrain control module (PCM)does not see 12 volts at this input when the ASDshould be activated, it will set a Diagnostic TroubleCode (DTC).

BATTERY VOLTAGE—PCM INPUTThe battery voltage input provides power to the

powertrain control module (PCM). It also informs thePCM what voltage level is supplied to the ignitioncoil and fuel injectors.

If battery voltage is low, the PCM will increase in-jector pulse width (period of time that the injector isenergized). This is done to compensate for the re-duced flow through the injector caused by the low-ered voltage.

BRAKE SWITCH—PCM INPUTWhen the brake light switch is activated, the pow-

ertrain control module (PCM) receives an input indi-cating that the brakes are being applied. Afterreceiving this input, the PCM maintains idle speed toa scheduled rpm through control of the idle air con-trol (IAC) motor. The brake switch input is also usedto operate the speed control system.

CAMSHAFT POSITION SENSOR—PCM INPUTA sync signal is provided by the camshaft position

sensor located in the distributor (Fig. 2). The syncsignal from this sensor works in conjunction with thecrankshaft position sensor to provide the powertraincontrol module (PCM) with inputs. This is done to es-tablish and maintain correct injector firing order.

Refer to Camshaft Position Sensor in Group 8D, Ig-nition System for more information.

DATA LINK CONNECTOR—PCM INPUTThe data link connector (diagnostic scan tool con-

nector) links the DRB scan tool with the powertraincontrol module (PCM). The data link connector is lo-cated in the engine compartment (Fig. 3). For opera-tion of the DRB scan tool, refer to the appropriatePowertrain Diagnostic Procedures service manual.

The data link connector uses two different pins onthe PCM. One is for Data Link Transmit and theother is for Data Link Receive.

Fig. 2 Camshaft Position Sensor


INTAKE MANIFOLD AIR TEMPERATURE SENSOR—PCM INPUT

The intake manifold air temperature sensor is in-stalled in the intake manifold with the sensor ele-ment extending into the air stream (Fig. 4). Thesensor provides an input voltage to the powertraincontrol module (PCM) indicating intake manifold airtemperature. The input is used along with inputsfrom other sensors to determine injector pulse width.As the temperature of the air-fuel stream in themanifold varies, the sensor resistance changes. Thisresults in a different input voltage to the PCM.

CRANKSHAFT POSITION SENSOR—PCM INPUTThis sensor is a hall effect device that detects

notches in the flywheel (manual transmission), orflexplate (automatic transmission).

This sensor is used to indicate to the powertraincontrol module (PCM) that a spark and or fuel injec-tion event is to be required. The output from thissensor, in conjunction with the camshaft position sen-sor signal, is used to differentiate between fuel injec-tion and spark events. It is also used to synchronizethe fuel injectors with their respective cylinders.

The sensor is bolted to the cylinder block near therear of the right cylinder head (Fig. 5).

Refer to Group 8D, Ignition System for more crank-shaft position sensor information.

The engine will not operate if the PCM does not re-ceive a crankshaft position sensor input.

ENGINE COOLANT TEMPERATURE SENSOR—PCMINPUT

The engine coolant temperature sensor is installednext to the thermostat housing (Fig. 6) and protrudesinto the water jacket. The sensor provides an inputvoltage to the powertrain control module (PCM) re-lating coolant temperature. The PCM uses this inputalong with inputs from other sensors to determine in-jector pulse width and ignition timing. As coolanttemperature varies, the coolant temperature sensor’sresistance changes. The change in resistance resultsin a different input voltage to the PCM.

When the engine is cold, the PCM will operate inOpen Loop cycle. It will demand slightly richer air-fuel mixtures and higher idle speeds. This is doneuntil normal operating temperatures are reached.

IGNITION CIRCUIT SENSE—PCM INPUTThe ignition circuit sense input tells the powertrain

control module (PCM) the ignition switch has ener-


Fig. 4 Air Temperature Sensor—Typical

Fig. 5 Crankshaft Position Sensor


gized the ignition circuit. Refer to the wiring dia-grams for circuit information.

MANIFOLD ABSOLUTE PRESSURE (MAP)SENSOR—PCM INPUT

The MAP sensor reacts to absolute pressure in theintake manifold. It provides an input voltage to thepowertrain control module (PCM). As engine loadchanges, manifold pressure varies. The change inmanifold pressure causes MAP sensor voltage tochange. The change in MAP sensor voltage results ina different input voltage to the PCM. The input volt-age level supplies the PCM with information aboutambient barometric pressure during engine start-up(cranking) and engine load while the engine is run-ning. The PCM uses this input along with inputsfrom other sensors to adjust air-fuel mixture.

The MAP sensor is mounted on the side of the en-gine throttle body (Fig. 7). The sensor is connected tothe throttle body with a rubber L-shaped fitting.

OXYGEN (O2S) SENSOR—PCM INPUTThe O2S sensor is located in the right exhaust

down pipe (Fig. 8). It provides an input voltage to thepowertrain control module (PCM) relating the oxygencontent of the exhaust gas. The PCM uses this infor-mation to fine tune the air-fuel ratio by adjusting in-jector pulse width.

The O2S sensor produces voltages from 0 to 1 volt.This voltage will depend upon the oxygen content ofthe exhaust gas in the exhaust manifold. When alarge amount of oxygen is present (caused by a leanair-fuel mixture), the sensor produces a low voltage.When there is a lesser amount present (rich air-fuelmixture), it produces a higher voltage. By monitoringthe oxygen content and converting it to electricalvoltage, the sensor acts as a rich-lean switch.

The oxygen sensor is equipped with a heating ele-ment that keeps the sensor at proper operating tem-perature during all operating modes. Maintaining

correct sensor temperature at all times allows thesystem to enter into closed loop operation sooner.

In Closed Loop operation, the powertrain controlmodule (PCM) monitors the O2S sensor input (alongwith other inputs). It then adjusts the injector pulsewidth accordingly. During Open Loop operation, thePCM ignores the O2S sensor input and adjusts injec-tor pulse width to a preprogrammed value (based onother sensor inputs).

OVERDRIVE/OVERRIDE SWITCHOn vehicles equipped with an automatic transmis-

sion and overdrive, the powertrain control module(PCM) regulates the 3-4 overdrive up-shift and down-shift through the overdrive solenoid. This solenoid is


Fig. 7 MAP Sensor—Typical

Fig. 8 Heated Oxygen Sensor—Typical


located in the transmission. An overdrive/overridepush-button switch is located on the instrumentpanel.

The PCM circuit for overdrive is controlled by in-puts from the engine coolant temperature sensor andvehicle speed sensor. If coolant temperature and ve-hicle speed are not within the preset PCM specifica-tions, the PCM will not allow the transmission toshift into overdrive. These preset PCM specificationsmust be met before the push-button switch will be al-lowed to control overdrive operation.

The overdrive/override push-button switch is nor-mally closed (overdrive allowed) when the lamp isnot illuminated. It opens (overdrive not allowed)when the operator presses the switch and the lamp isilluminated. The switch will revert to its normallyclosed position (lamp off) each time the ignitionswitch in turned on. The transmission downshifts ifthe operator presses the override switch while inoverdrive.

Refer to Group 21 for more transmission informa-tion.

PARK/NEUTRAL SWITCH—PCM INPUTThe park/neutral switch is located on the transmis-

sion housing and provides an input to the powertraincontrol module (PCM). This will indicate that the au-tomatic transmission is in Park, Neutral or a drivegear selection. This input is used to determine idlespeed (varying with gear selection), fuel injectorpulse width, ignition timing advance and vehiclespeed control operation. Refer to Group 21, Transmis-sions, for testing, replacement and adjustment infor-mation.

POWER GROUNDThe power ground is used to control ground circuits

for the following powertrain control module (PCM)loads:• Generator Field Winding• 8 volt (PCM) power supply• Fuel Injectors• Ignition Coil

SCI RECEIVE—PCM INPUTSCI Receive is the serial data communication re-

ceive circuit for the DRB scan tool. The powertraincontrol module (PCM) receives data from the DRBthrough the SCI Receive circuit.

SPEED CONTROL—PCM INPUTThe speed control system provides three separate

inputs to the powertrain control module (PCM); On/Off, Set and Resume. The On/Off input informs thePCM that the speed control system has been acti-vated. The Set input informs the PCM that a fixed

vehicle speed has been selected. The Resume inputindicates to the PCM that the previous fixed speed isrequested.

The speed control operating range is from 50 km/hto 142 km/h (35 to 85 mph). Inputs that effect speedcontrol operation are:• Brake switch position• Park/neutral switch• Vehicle speed sensor• Throttle position sensor

Refer to Group 8H for further speed control infor-mation.

SENSOR RETURN—PCM INPUTSensor Return provides a low noise ground refer-

ence for all system sensors.

THROTTLE POSITION SENSOR (TPS)—PCM INPUTThe throttle position sensor (TPS) is mounted on

the throttle body (Fig. 9). The TPS is a variable re-sistor that provides the powertrain control module(PCM) with an input signal (voltage) that representsthrottle blade position. The sensor is connected to thethrottle blade shaft. As the position of the throttleblade changes, the resistance of the TPS changes.

The PCM supplies approximately 5 volts to theTPS. The TPS output voltage (input signal to thePCM) represents the throttle blade position. ThePCM receives an input signal voltage from the TPS.This will vary in an approximate range of from 1 voltat minimum throttle opening (idle), to 4 volts at wideopen throttle. Along with inputs from other sensors,the PCM uses the TPS input to determine currentengine operating conditions. In response to engineoperating conditions, the PCM will adjust fuel injec-tor pulse width and ignition timing.

VEHICLE SPEED SENSOR—PCM INPUTThe speed sensor (Fig. 10) is located in the exten-

sion housing of the transmission (2WD) or on thetransfer case extension housing (4WD). The sensorinput is used by the powertrain control module(PCM) to determine vehicle speed and distance trav-eled.

The speed sensor generates 8 pulses per sensorrevolution. These signals, in conjunction with aclosed throttle signal from the throttle position sen-sor, indicate a closed throttle deceleration to thePCM. When the vehicle is stopped at idle, a closedthrottle signal is received by the PCM, but a speedsensor signal is not received.

Under deceleration conditions, the PCM adjusts theidle air control (IAC) motor to maintain a desiredMAP value. Under idle conditions, the PCM adjuststhe IAC motor to maintain a desired engine speed.


AIR CONDITIONING (A/C) CLUTCH RELAY—PCMOUTPUT

The powertrain control module (PCM) activates theA/C compressor through the A/C clutch relay. ThePCM regulates A/C compressor operation by switch-ing the ground circuit for the A/C clutch relay on andoff. The relay is located in the power distributioncenter (PDC) (Fig. 11). For the location of the relaywithin the PDC, refer to label under PDC cover.

When the PCM receives a request for A/C from theA/C evaporator switch, it will adjust the idle air con-trol (IAC) motor position. This is done to increaseidle speed. The PCM will then activate the A/C clutchthrough the A/C clutch relay. The PCM then adjuststhe idle air control (IAC) stepper motor position tocompensate for increased engine load from the A/Ccompressor.

By switching the ground path for the relay on andoff, the PCM is able to cycle the A/C compressorclutch. This is based on changes in engine operatingconditions. If, during A/C operation, the PCM senseslow idle speeds or a wide open throttle condition, itwill de-energize the relay. This prevents A/C clutchengagement. The relay will remain de-energized untilthe idle speed increases, or the wide open throttlecondition exceeds 15 seconds, or no longer exists. ThePCM will also de-energize the relay if engine coolanttemperature exceeds 125°C (257°F).

IDLE AIR CONTROL (IAC) MOTOR—PCM OUTPUTThe IAC motor is mounted to the back of the throt-

tle body (Fig. 9) and is controlled by the powertraincontrol module (PCM).

The throttle body has an air control passage thatprovides air for the engine at idle (the throttle plateis closed). The IAC motor pintle protrudes into theair control passage (Fig. 12) and regulates air flowthrough it. Based on various sensor inputs, the pow-ertrain control module (PCM) adjusts engine idlespeed by moving the IAC motor pintle in and out ofthe air control passage. The IAC motor is positionedwhen the ignition key is turned to the On position.

Fig. 9 Throttle Position Sensor and IAC Motor—Typical





AUTO SHUTDOWN (ASD) RELAY—PCM OUTPUTThe ASD relay is located in the power distribution

center (PDC) (Fig. 11). For the location of this relaywithin the PDC, refer to label under PDC cover.

The ASD supplies battery voltage to the fuel pump,fuel injector, ignition coil, generator field windingand oxygen (O2S) sensor heating element. Theground circuit for the coil in the ASD relay is con-trolled by the powertrain control module (PCM). ThePCM operates the relay by switching the ground cir-cuit on and off.

The fuel pump relay is controlled by the PCMthrough same circuit that the ASD relay is con-trolled.

GENERATOR FIELD—PCM OUTPUTThe powertrain control module (PCM) regulates the

charging system voltage within a range of 12.9 to15.0 volts. Refer to Group 8A for charging system in-formation.

GENERATOR LAMP—PCM OUTPUTIf the powertrain control module (PCM) senses a

low charging condition in the charging system, it willilluminate the generator lamp on the instrumentpanel. For example, during low idle with all accesso-ries turned on, the lamp may momentarily go on.Once the PCM corrects idle speed to a higher rpm,the lamp will go out. Refer to Group 8A for chargingsystem information.

EGR (EXHAUST GAS RECIRCULATION) VALVECONTROL SOLENOID—PCM OUTPUT

Refer to Group 25, Emission Control System for in-formation. See EGR (Exhaust Gas Recirculation) Sys-tem.

DATA LINK CONNECTOR—PCM OUTPUTRefer to the previous paragraphs on Data Link

Connector—PCM Input for information.

EVAP CANISTER PURGE SOLENOID—PCMOUTPUT

Refer to Group 25, Emission Control System. SeeEVAP Canister Purge Solenoid.

FUEL INJECTORS—PCM OUTPUTThe fuel injectors are attached to the fuel rail (Fig.

13). 5.2L engines use eight individual injectors foreach cylinder.

The nozzle ends of the injectors are positioned intoopenings in the intake manifold just above the intakevalve ports of the cylinder head. The engine wiringharness connector for each fuel injector is equippedwith an attached numerical tag (INJ 1, INJ 2 etc.).This is used to identify each fuel injector.

The injectors are energized individually in a se-quential order by the powertrain control module(PCM). The PCM will adjust injector pulse width byswitching the ground path to each individual injectoron and off. Injector pulse width is the period of timethat the injector is energized. The PCM will adjustinjector pulse width based on various inputs it re-ceives.

During start up, battery voltage is supplied to theinjectors through the ASD relay. When the engine isoperating, voltage is supplied by the charging sys-tem. The PCM determines injector pulse width basedon various inputs.

MALFUNCTION INDICATOR LAMP—PCM OUTPUTThe malfunction indicator lamp illuminates each

time the ignition key is turned on. It will stay on forapproximately three seconds as a bulb test. The lampis displayed on the instrument panel as the CHECKENGINE lamp (Fig. 14).

If the powertrain control module (PCM) receives anincorrect signal, or no signal from certain sensors oremission related systems, the lamp is turned on. Thisis a warning that the PCM has recorded a system orsensor malfunction. In some cases, when a problem isdeclared, the PCM will go into a limp-in mode. Thisis an attempt to keep the system operating. It signalsan immediate need for service.

The lamp can also be used to display a DiagnosticTrouble Code (DTC). Cycle the ignition switch On-Off-On-Off-On within three seconds and any codesstored in the PCM memory will be displayed. This is

Fig. 12 Throttle Body Air Control Passage


done in a series of flashes representing digits. Referto On-Board Diagnostics in the General Diagnosissection of this group for more information.

IGNITION COIL—PCM OUTPUTSystem voltage is supplied to the ignition coil pos-

itive terminal. The powertrain control module (PCM)operates the ignition coil. Base (initial) ignitiontiming is not adjustable. The PCM adjusts ignitiontiming to meet changing engine operating conditions.

The ignition coil is located near the front of theright cylinder head (Fig. 15).

SCI TRANSMIT—PCM OUTPUTSCI Transmit is the serial data communication

transmit circuit for the DRB scan tool. The power-

train control module (PCM) transmits data to theDRB through the SCI Transmit circuit.

SHIFT INDICATOR—PCM OUTPUTVehicles equipped with manual transmissions have

an Up-Shift indicator lamp. The lamp is controlled bythe powertrain control module (PCM). The lamp illu-minates on the instrument panel to indicate whenthe driver should shift to the next highest gear forbest fuel economy. The PCM will turn the lamp OFFafter 3 to 5 seconds if the shift of gears is not per-formed. The up-shift lamp will remain off until thevehicle stops accelerating and is brought back torange of up-shift lamp operation. This will also hap-pen if vehicle is shifted into fifth gear.

The indicator lamp is normally illuminated whenthe ignition switch is turned on and it is turned offwhen the engine is started up. With the engine run-ning, the lamp is turned on/off depending upon en-gine speed and load.

SPEED CONTROL—PCM OUTPUTSpeed control operation is regulated by the power-

train control module (PCM). The PCM controls thevacuum to the throttle actuator through the speedcontrol vacuum and vent solenoids. Refer to Group8H for Speed Control Information.

TACHOMETER—PCM OUTPUTThe powertrain control module (PCM) supplies en-

gine rpm values to the instrument cluster tachome-ter. Refer to Group 8E for tachometer information.

OPEN LOOP/CLOSED LOOP MODES OFOPERATION

As input signals to the powertrain control module(PCM) change, the PCM adjusts its response to theoutput devices. For example, the PCM must calculatedifferent injector pulse width and ignition timing foridle than it does for wide open throttle (WOT). There

Fig. 13 Fuel Injectors—Typical


Fig. 15 Ignition Coil


are several different modes of operation that deter-mine how the PCM responds to the various input sig-nals.

MODES• Open Loop• Closed Loop

During Open Loop modes, the powertrain controlmodule (PCM) receives input signals and respondsonly according to preset PCM programming. Inputfrom the oxygen (O2S) sensor is not monitored dur-ing Open Loop modes.

During Closed Loop modes, the PCM will monitorthe oxygen (O2S) sensor input. This input indicatesto the PCM whether or not the calculated injectorpulse width results in the ideal air-fuel ratio. Thisratio is 14.7 parts air-to-1 part fuel. By monitoringthe exhaust oxygen content through the O2S sensor,the PCM can fine tune the injector pulse width. Thisis done to achieve optimum fuel economy combinedwith low emission engine performance.

The fuel injection system has the following modesof operation:• Ignition switch ON• Engine start-up (crank)• Engine warm-up• Idle• Cruise• Acceleration• Deceleration• Wide open throttle (WOT)• Ignition switch OFF

The ignition switch On, engine start-up (crank), en-gine warm-up, acceleration, deceleration and wideopen throttle modes are Open Loop modes. The idleand cruise modes, (with the engine at operating tem-perature) are Closed Loop modes.

IGNITION SWITCH (KEY-ON) MODEThis is an Open Loop mode. When the fuel system

is activated by the ignition switch, the following ac-tions occur:• The powertrain control module (PCM) pre-posi-tions the idle air control (IAC) motor.• The PCM determines atmospheric air pressurefrom the MAP sensor input to determine basic fuelstrategy.• The PCM monitors the engine coolant temperaturesensor input. The PCM modifies fuel strategy basedon this input.• Intake manifold air temperature sensor input ismonitored• Throttle position sensor (TPS) is monitored• The auto shutdown (ASD) relay is energized by thePCM for approximately three seconds.• The fuel pump is energized through the fuel pumprelay by the PCM. The fuel pump will operate for ap-

proximately three seconds unless the engine is oper-ating or the starter motor is engaged.• The O2S sensor heater element is energizedthrough the fuel pump relay. The O2S sensor input isnot used by the PCM to calibrate air-fuel ratio dur-ing this mode of operation.• The up-shift indicator lamp is illuminated (manualtransmission only).

ENGINE START-UP MODEThis is an Open Loop mode. The following actions

occur when the starter motor is engaged.The powertrain control module (PCM) receives in-

puts from:• Battery voltage• Engine coolant temperature sensor• Crankshaft position sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Starter motor relay• Camshaft position sensor signal

The PCM monitors the crankshaft position sensor.If the PCM does not receive a crankshaft positionsensor signal within 3 seconds of cranking the en-gine, it will shut down the fuel injection system.

The fuel pump is activated by the PCM throughthe fuel pump relay.

Voltage is applied to the fuel injectors with thePCM. The PCM will then control the injection se-quence and injector pulse width by turning theground circuit to each individual injector on and off.

The PCM determines the proper ignition timing ac-cording to input received from the crankshaft posi-tion sensor.

ENGINE WARM-UP MODEThis is an Open Loop mode. During engine warm-

up, the powertrain control module (PCM) receives in-puts from:• Battery voltage• Crankshaft position sensor• Engine coolant temperature sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)• Park/neutral switch (gear indicator signal—auto.trans. only)• Air conditioning select signal (if equipped)• Air conditioning request signal (if equipped)

Based on these inputs the following occurs:• Voltage is applied to the fuel injectors with thepowertrain control module (PCM). The PCM willthen control the injection sequence and injector pulsewidth by turning the ground circuit to each individ-ual injector on and off.


• The PCM adjusts engine idle speed through theidle air control (IAC) motor and adjusts ignition tim-ing.• The PCM operates the A/C compressor clutchthrough the clutch relay. This is done if A/C has beenselected by the vehicle operator and requested by theA/C thermostat.• If the vehicle has a manual transmission, the up-shift lamp is operated by the PCM.• When the engine has reached operating tempera-ture, the PCM will begin monitoring O2S sensor in-put. The system will then leave the warm-up modeand go into closed loop operation.

IDLE MODEWhen the engine is at operating temperature, this

is a Closed Loop mode. At idle speed, the powertraincontrol module (PCM) receives inputs from:• Air conditioning select signal (if equipped)• Air conditioning request signal (if equipped)• Battery voltage• Crankshaft position sensor• Engine coolant temperature sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)• Battery voltage• Park/neutral switch (gear indicator signal—auto.trans. only)• Oxygen sensor

Based on these inputs, the following occurs:• Voltage is applied to the fuel injectors with thepowertrain control module (PCM). The PCM willthen control injection sequence and injector pulsewidth by turning the ground circuit to each individ-ual injector on and off.• The PCM monitors the O2S sensor input and ad-justs air-fuel ratio by varying injector pulse width. Italso adjusts engine idle speed through the idle aircontrol (IAC) motor.• The PCM adjusts ignition timing by increasingand decreasing spark advance.• The PCM operates the A/C compressor clutchthrough the clutch relay. This happens if A/C hasbeen selected by the vehicle operator and requestedby the A/C thermostat.

CRUISE MODEWhen the engine is at operating temperature, this

is a Closed Loop mode. At cruising speed, the power-train control module (PCM) receives inputs from:• Air conditioning select signal (if equipped)• Air conditioning request signal (if equipped)• Battery voltage• Engine coolant temperature sensor• Crankshaft position sensor

• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)• Park/neutral switch (gear indicator signal—auto.trans. only)• Oxygen (O2S) sensor

Based on these inputs, the following occurs:• Voltage is applied to the fuel injectors with thePCM. The PCM will then adjust the injector pulsewidth by turning the ground circuit to each individ-ual injector on and off.• The PCM monitors the O2S sensor input and ad-justs air-fuel ratio. It also adjusts engine idle speedthrough the idle air control (IAC) motor.• The PCM adjusts ignition timing by turning theground path to the coil on and off.• The PCM operates the A/C compressor clutchthrough the clutch relay. This happens if A/C hasbeen selected by the vehicle operator and requestedby the A/C thermostat.

ACCELERATION MODEThis is an Open Loop mode. The powertrain control

module (PCM) recognizes an abrupt increase inthrottle position or MAP pressure as a demand forincreased engine output and vehicle acceleration. ThePCM increases injector pulse width in response to in-creased throttle opening.

DECELERATION MODEWhen the engine is at operating temperature, this

is an Open Loop mode. During hard deceleration, thepowertrain control module (PCM) receives the follow-ing inputs.• Air conditioning select signal (if equipped)• Air conditioning request signal (if equipped)• Battery voltage• Engine coolant temperature sensor• Crankshaft position sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)• Park/neutral switch (gear indicator signal—auto.trans. only)

If the vehicle is under hard deceleration with theproper rpm and closed throttle conditions, the PCMwill ignore the oxygen sensor input signal. The PCMwill enter a fuel cut-off strategy in which it will notsupply battery voltage to the injectors. If a hard de-celeration does not exist, the PCM will determine theproper injector pulse width and continue injection.

Based on the above inputs, the PCM will adjust en-gine idle speed through the idle air control (IAC) mo-tor.


The PCM adjusts ignition timing by turning theground path to the coil on and off.

The PCM opens the ground circuit to the A/Cclutch relay to disengage the A/C compressor clutch.This is done until the vehicle is no longer under de-celeration (if the A/C system is operating).

WIDE OPEN THROTTLE MODEThis is an Open Loop mode. During wide open

throttle operation, the powertrain control module(PCM) receives the following inputs.• Battery voltage• Crankshaft position sensor• Engine coolant temperature sensor• Intake manifold air temperature sensor• Manifold absolute pressure (MAP) sensor• Throttle position sensor (TPS)• Camshaft position sensor signal (in the distribu-tor)

During wide open throttle conditions, the followingoccurs:• Voltage is applied to the fuel injectors with thepowertrain control module (PCM). The PCM willthen control the injection sequence and injector pulsewidth by turning the ground circuit to each individ-ual injector on and off. The PCM ignores the oxygensensor input signal and provides a predeterminedamount of additional fuel. This is done by adjustinginjector pulse width.• The PCM adjusts ignition timing by turning theground path to the coil on and off.• The PCM opens the ground circuit to the A/Cclutch relay to disengage the A/C compressor clutch.This will be done for approximately 15 seconds if theair conditioning system is operating.

If the vehicle has a manual transmission, the up-shift lamp is operated by the PCM.

When the PCM senses wide open throttle conditionthrough the throttle position sensor (TPS), it willprovide a ground for the EGR solenoid. This will pre-vent any EGR functions.

IGNITION SWITCH OFF MODEWhen ignition switch is turned to OFF position,

the PCM stops operating the injectors, ignition coil,ASD relay and fuel pump relay.

THROTTLE BODYFiltered air from the air cleaner enters the intake

manifold through the throttle body (Fig. 16). Fueldoes not enter the intake manifold through the throt-tle body. Fuel is sprayed into the manifold by the fuelinjectors. The throttle body is mounted on the intakemanifold. It contains an air control passage (Fig. 17)controlled by an idle air control (IAC) motor. The aircontrol passage is used to supply air for idle condi-tions. A throttle valve (plate) is used to supply air forabove idle conditions.

The throttle position sensor (TPS), idle air control(IAC) motor and manifold absolute pressure sensor(MAP) are attached to the throttle body. The acceler-ator pedal cable, speed control cable and transmis-sion control cable (when equipped) are connected tothe throttle arm.


FUEL RAILThe fuel rail supplies fuel to the injectors and is

mounted to the intake manifold (Fig. 18). The fuelpressure regulator is no longer attached to the fuel

Fig. 16 Throttle Body—Typical

Fig. 17 Air Control Passage


rail. It is now a part of the fuel pump module. Thefuel pressure test port is integral with the rail andthe rail is not repairable.

FUEL PRESSURE REGULATORThe fuel pressure regulator is no longer attached to

the fuel rail. It is now a part of the fuel pump mod-ule. Refer to the Fuel Delivery section of this groupfor an operational description.

Fig. 18 Fuel Rail—Typical


MULTI-PORT FUEL INJECTION (MFI)—5.2L V-8 ENGINE—GENERAL DIAGNOSIS

INDEX

page page

Automatic Shutdown (ASD) Relay Testing . . . . . . . 71Camshaft Position Sensor Testing . . . . . . . . . . . . . 71Crankshaft Position Sensor Test . . . . . . . . . . . . . . 73Diagnostic Trouble Code (DTC) . . . . . . . . . . . . . . . 81DRB Scan Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . 80Engine Coolant Temperature Sensor Test . . . . . . . 71Fuel Injector Test . . . . . . . . . . . . . . . . . . . . . . . . . 77Fuel Pump Pressure Test . . . . . . . . . . . . . . . . . . . 77Fuel Pump Relay Testing . . . . . . . . . . . . . . . . . . . 71Idle Air Control (IAC) Motor Test . . . . . . . . . . . . . . 75Intake Manifold Air Temperature Sensor Test . . . . . 71Manifold Absolute Pressure (MAP) Sensor Test . . . 72

On-Board Diagnostics (OBD) . . . . . . . . . . . . . . . . . 77Oxygen (O2S) Sensor Heating Element Test . . . . . 75PCM System Schematics . . . . . . . . . . . . . . . . . . . 69Powertrain Control Module (PCM) 60-Way

Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69Relays—Operation/Testing . . . . . . . . . . . . . . . . . . 76Starter Motor Relay Test . . . . . . . . . . . . . . . . . . . . 77Throttle Body Minimum Air Flow Check . . . . . . . . . 73Throttle Position Sensor (TPS) Test . . . . . . . . . . . . 73Vehicle Speed Sensor Test . . . . . . . . . . . . . . . . . . 75Visual Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . 66

VISUAL INSPECTIONA visual inspection for loose, disconnected, or incor-

rectly routed wires and hoses should be made. Thisshould be done before attempting to diagnose or ser-vice the fuel injection system. A visual check willhelp spot these faults and save unnecessary test anddiagnostic time. A thorough visual inspection will in-clude the following checks:

(1) Verify that the 60-way connector is fully in-serted into the connector of the powertrain controlmodule (PCM) (Fig. 1). Verify that the connectormounting bolt is tightened to 4 Nzm (35 in. lbs.)torque.

(2) Inspect the battery cable connections. Be surethat they are clean and tight.

(3) Inspect fuel pump relay and air conditioningcompressor clutch relay (if equipped). Inspect theASD relay connections. Inspect starter motor relayconnections. Inspect relays for signs of physical dam-age and corrosion. The relays are located in thepower distribution center (PDC) (Fig. 2). For the lo-cation of the relays within the PDC, refer to label un-der PDC cover.

(4) Inspect ignition coil connections. Verify that coilsecondary cable is firmly connected to coil (Fig. 3).

(5) Verify that distributor cap is correctly attachedto distributor. Be sure that spark plug cables arefirmly connected to the distributor cap and the sparkplugs are in their correct firing order. Be sure thatcoil cable is firmly connected to distributor cap and

Fig. 1 Powertrain Control Module (PCM)


14 - 66 FUEL SYSTEM GENERAL DIAGNOSIS—5.2L V-8 ENGINE ZJ

coil. Be sure that camshaft position sensor wire con-nector (at the distributor) is firmly connected to har-ness connector. Inspect spark plug condition. Refer toGroup 8D, Ignition. Connect vehicle to an oscilloscopeand inspect spark events for fouled or damaged sparkplugs or cables.

(6) Verify that generator output wire, generatorconnector and ground wire are firmly connected tothe generator.

(7) Inspect the system body grounds for loose ordirty connections. Refer to Group 8W, Wiring for lo-cation of body ground connections.

(8) Verify positive crankcase ventilation (PCV)valve operation. Refer to Group 25, Emission ControlSystem for additional information. Verify PCV valvehose is firmly connected to PCV valve and manifold(Fig. 4).

(9) Inspect fuel line/tube quick-connect fitting-to-fuel rail connections. Refer to Quick-Connect Fittingsin this group for procedures.

(10) Verify that hose connections to all ports ofvacuum fittings on intake manifold are tight and notleaking.

(11) Inspect accelerator cable, transmission throttlecable (if equipped) and cruise control cable connec-tions (if equipped). Check their connections to thethrottle arm of throttle body for any binding or re-strictions.

(12) If equipped with vacuum brake booster, verifythat vacuum booster hose is firmly connected to fit-ting on intake manifold. Also check connection tobrake vacuum booster.

(13) Inspect the air cleaner inlet and air cleaner el-ement for dirt or restrictions.

(14) Inspect radiator grille area, radiator fins andair conditioning condenser for restrictions.

(15) Verify that the intake manifold air tempera-ture sensor wire connector is firmly connected to har-ness connector (Fig. 5).

(16) Verify that MAP sensor electrical connector isfirmly connected to MAP sensor (Fig. 6). Also verifythat rubber L-shaped fitting from MAP sensor to thethrottle body is firmly connected (Fig. 7).

(17) Verify that fuel injector wire harness connec-tors are firmly connected to injectors in the correctfiring order. Each harness connector is numericallytagged with the injector number (INJ 1, INJ 2 etc.) ofits corresponding fuel injector and cylinder number.

(18) Verify harness connectors are firmly connectedto idle air control (IAC) motor, throttle position sen-sor (TPS) and manifold absolute pressure (MAP) sen-sor (Fig. 6).

(19) Verify that wire harness connector is firmlyconnected to the engine coolant temperature sensor(Fig. 8).

(20) Raise and support the vehicle.(21) Verify that oxygen sensor wire connector is

firmly connected to the sensor. Inspect sensor andconnector for damage (Fig. 9).

Fig. 3 Ignition Coil

Fig. 4 PCV Valve Hose Connections


ZJ FUEL SYSTEM GENERAL DIAGNOSIS—5.2L V-8 ENGINE 14 - 67

(22) Inspect for pinched or leaking fuel lines/tubes.Inspect for pinched, cracked or leaking fuel hoses.Refer to Quick-Connect Fittings in this group for pro-cedures.

(23) Inspect for exhaust system restrictions suchas pinched exhaust pipes, collapsed muffler orplugged catalytic convertor.

(24) If equipped with automatic transmission, ver-ify that electrical harness is firmly connected to park/neutral switch. Refer to Automatic Transmissionsection of Group 21.


Fig. 7 Rubber L-Shaped Fitting—MAP Sensor-to-Throttle Body




(25) Verify that the harness connector is firmlyconnected to the vehicle speed sensor (Fig. 10).

(26) Verify that fuel pump/gauge sender unit wireconnector is firmly connected to harness connector.

(27) Inspect fuel hoses at fuel filter for cracks orleaks.

(28) Inspect transmission torque convertor housing(automatic transmission) or clutch housing (manualtransmission) for damage to timing ring on driveplate/flywheel.

(29) Verify that battery cable and solenoid feedwire connections to the starter solenoid are tight andclean. Inspect for chaffed wires or wires rubbing upagainst other components.

POWERTRAIN CONTROL MODULE (PCM) 60-WAYCONNECTOR

For PCM 60-way connector wiring schematics, referto Group 8W, Wiring Diagrams.

PCM SYSTEM SCHEMATICSA powertrain control system schematics for the

5.2L (V-8) engine is shown in figure 11.The schematic is displayed as a quick reference

only. It is not intended to be all-inclusive. Refer tothe Wiring Diagrams section for detailed information.Fig. 10 Vehicle Speed Sensor—Typical


Fig

.11

Sys

tem

Sch

emat

ic—

5.2L

Eng

ine


AUTOMATIC SHUTDOWN (ASD) RELAY TESTINGTo perform a complete test of the ASD relay and its

circuitry, refer to the DRB scan tool and appropriatePowertrain Diagnostics Procedures manual. To testthe relay only, refer to Relays—Operation/Testing inthis section of the group.

CAMSHAFT POSITION SENSOR TESTINGRefer to Group 8D, Ignition Systems for testing.

ENGINE COOLANT TEMPERATURE SENSOR TESTTo perform a complete test of this sensor and its


(1) Disconnect wire harness connector from coolanttemperature sensor (Fig. 12).

Engines with air conditioning: When removingthe connector from sensor, do not pull directly on wir-ing harness. Fabricate an L-shaped hook tool from acoat hanger (approximately eight inches long). Placethe hook part of tool under the connector for removal.The connector is snapped onto the sensor. It is notequipped with a lock type tab.

(2) Test the resistance of the sensor with a high in-put impedance (digital) volt-ohmmeter. The resis-tance (as measured across the sensor terminals)should be less than 1340 ohms with the enginewarm. Refer to the Coolant Temperature sensor/In-take Air Temperature sensor resistance chart. Re-place the sensor if it is not within the range ofresistance specified in the chart.

(3) Test continuity of the wire harness. Do this be-tween the powertrain control module (PCM) wireharness connector terminal 2 and the sensor connec-tor terminal. Also test continuity of wire harness ter-minal 4 to the sensor connector terminal. Repair thewire harness if an open circuit is indicated.

(4) After tests are completed, connect electricalconnector to sensor. The sensor connector is symmet-rical (not indexed). It can be installed to the sensorin either direction.

FUEL PUMP RELAY TESTINGFor testing this relay, refer to Relays—Operation/

Testing in this section of the group.

INTAKE MANIFOLD AIR TEMPERATURE SENSORTEST


(1) Disconnect the wire harness connector from theintake manifold air temperature sensor (Fig. 13).

(2) Test the resistance of the sensor with an inputimpedance (digital) volt-ohmmeter. The resistance (asmeasured across the sensor terminals) should be lessthan 1340 ohms with the engine warm. Refer to theCoolant Temperature sensor/Intake Air Temperaturesensor resistance chart. Replace the sensor if it is notwithin the range of resistance specified in the chart.

(3) Test the resistance of the wire harness. Do thisbetween the powertrain control module (PCM) wireharness connector terminal 21 and the sensor con-nector terminal. Also check between terminal 4 to thesensor connector terminal. Repair the wire harnessas necessary if the resistance is greater than 1 ohm.


SENSOR RESISTANCE (OHMS)—COOLANTTEMPERATURE SENSOR/INTAKE AIR

TEMPERATURE SENSOR


MANIFOLD ABSOLUTE PRESSURE (MAP) SENSORTEST

To perform a complete test of MAP sensor (Fig. 14)and its circuitry, refer to DRB scan tool and appro-priate Powertrain Diagnostics Procedures manual. Totest the MAP sensor only, refer to the following:

(1) Inspect the rubber L-shaped fitting from theMAP sensor to the throttle body (Fig. 15). Repair asnecessary.

CAUTION: When testing the MAP sensor, be surethat the harness wires are not damaged by the testmeter probes.

(2) Test the MAP sensor output voltage at theMAP sensor connector between terminals A and B(Fig. 16). With the ignition switch ON and the engine

OFF, output voltage should be 4-to-5 volts. The volt-age should drop to 1.5-to-2.1 volts with a hot, neutralidle speed condition.

(3) Test powertrain control module (PCM) pin-1 forthe same voltage described above to verify the wireharness condition. Repair as necessary.

(4) Test MAP sensor supply voltage at sensor con-nector between terminals A and C (Fig. 16) with theignition ON. The voltage should be approximately 5volts (60.5V). Five volts (60.5V) should also be atterminal 6 of the powertrain control module (PCM)wire harness connector. Repair or replace the wireharness as necessary.

(5) Test the MAP sensor ground circuit at sensorconnector terminal A (Fig. 16) and PCM connectorterminal/pin-4. Repair the wire harness if necessary.

(6) Test the MAP sensor ground circuit at the PCM



Fig. 15 Rubber L-Shaped Fitting—MAP Sensor-to-Throttle Body

Fig. 16 MAP Sensor Connector Terminals—Typical


connector between terminal/pin-4 and terminal/pin-11 with an ohmmeter. If the ohmmeter indicatesan open circuit, inspect for a defective sensor groundconnection. Refer to Group 8W, Wiring Diagrams forlocation of this connection. If the ground connectionis good, replace the PCM. If terminal/pin-4 has ashort circuit to 12 volts +, correct this condition be-fore replacing the PCM.

CRANKSHAFT POSITION SENSOR TESTTo perform a complete test of this sensor (Fig. 17)

and its circuitry, refer to the DRB scan tool and ap-propriate Powertrain Diagnostics Procedures manual.To test the sensor only, refer to the following:

(1) Near the rear of the right cylinder head, dis-connect the sensor pigtail harness connector from themain wiring harness.

(2) Place an ohmmeter across terminals B and C(Fig. 18). Ohmmeter should be set to 1K-to-10K scalefor this test. The meter reading should be open (noresistance). Replace sensor if a low resistance is indi-cated.

THROTTLE POSITION SENSOR (TPS) TESTTo perform a complete test of the TPS and its cir-

cuitry, refer to the DRB scan tool and appropriatePowertrain Diagnostics Procedures manual. To testthe TPS only, refer to the following:

The TPS can be tested with a digital voltmeter.The center terminal of the TPS is the output termi-nal (Fig. 19).

With the ignition key in the ON position, check theTPS output voltage at the center terminal wire of theconnector. Check this at idle (throttle plate closed)

and at wide open throttle (WOT). At idle, TPS outputvoltage should must be greater than 200 millivolts.At wide open throttle, TPS output voltage must beless than 4.8 volts. The output voltage should in-crease gradually as the throttle plate is slowlyopened from idle to WOT.

THROTTLE BODY MINIMUM AIR FLOW CHECK

5.2L V-8 ENGINE ONLYThe following test procedure has been developed to

check throttle body calibrations for correct idle condi-tions. The procedure should be used to diagnose thethrottle body for conditions that may cause idle prob-lems. This procedure should be used only afternormal diagnostic procedures have failed toproduce results that indicate a throttle body re-lated problem. Be sure to check for proper op-eration of the idle air control motor beforeperforming this test.

Fig. 17 Crankshaft Position Sensor

Fig. 18 Sensor Wiring Connector

Fig. 19 TPS Connector and IAC Motor—Typical


A special fixed orifice tool (number 6714) (Fig. 20)must be used for the following test.

(1) Start the engine and bring to operating temper-ature. Be sure all accessories are off before perform-ing this test.

(2) Shut off the engine and remove the air intaketube at the throttle body.

(3) Disconnect the vacuum line at the PCV valve(Fig. 21).

(4) Install the 0.185 inch orifice tool (number 6714)into the disconnected vacuum line in place of thePCV valve (Fig. 21).

(5) Disconnect the idle purge vacuum line from fit-ting at throttle body. This vacuum line is located onthe front of throttle body next to the MAP sensor(Fig. 22). Cap the fitting at throttle body after vac-uum line has been removed.

(6) Connect the DRB scan tool to the data link con-nector (Fig. 23) on the vehicle. Refer to the appropri-ate Powertrain Diagnostic Procedures service manualfor DRB operation.

(7) Start the engine.(8) Using the DRB scan tool, scroll through the

menus as follows: select—System, select—Engine, se-lect—Fuel and Ignition, select—Actuator Tests, se-lect—Engine rpm and select—Minimum Air Flow.

The DRB scan tool will count down to stabilize theidle rpm and display the minimum air flow idle rpm.The idle rpm should be between 500 and 900 rpm.If the idle speed is outside of these specifications, re-place the throttle body. Refer to Throttle Body in theComponent Removal/Installation section of thisgroup.

(9) Disconnect the DRB scan tool from the vehicle.(10) Remove cap from idle purge fitting at throttle

body and install vacuum line.

Fig. 20 Fixed Orifice Tool

Fig. 21 Install Orifice Tool

Fig. 22 Idle Purge Line

Fig. 23 Data Link Connector Location


(11) Remove orifice tool and connect vacuum lineto PCV valve.

(12) Install air cleaner element housing.

VEHICLE SPEED SENSOR TESTTo perform a complete test of the sensor and its cir-

cuitry, refer to DRB scan tool and appropriate Pow-ertrain Diagnostics Procedures manual.

OXYGEN (O2S) SENSOR HEATING ELEMENT TESTTo perform a complete test of O2S sensor and its

circuitry, refer to DRB scan tool and appropriatePowertrain Diagnostics Procedures manual. To testthe O2S only, refer to the following:

The O2S sensor is located on the right exhaustdown pipe (Fig. 24). The O2S heating element can betested with an ohmmeter as follows:

Disconnect the O2S sensor connector. Connect theohmmeter test leads across the white wire terminalsof the sensor connector. Resistance should be be-tween 5 and 7 ohms. Replace the sensor if the ohm-meter displays an infinity (open) reading.

IDLE AIR CONTROL (IAC) MOTOR TESTTo perform a complete test of IAC motor (Fig. 19)

and its circuitry, refer to DRB scan tool and appro-priate Powertrain Diagnostics Procedures manual. Totest the IAC motor only, special IAC motor exercisertool number 7558 (Fig. 25) may be used.

CAUTION: Proper safety precautions must be takenwhen testing the IAC motor.

• Set the parking brake and block the drive wheels• Route all tester cables away from the cooling fans,drive belt, pulleys and exhaust components• Provide proper ventilation while operating the en-gine• Always return the engine idle speed to normal be-fore disconnecting the exerciser tool

(1) With the ignition OFF, disconnect the IAC mo-tor wire connector at throttle body (Fig. 25).

(2) Plug the exerciser tool (7558) harness connectorinto the IAC motor (Fig. 25).

(3) Connect the red clip of exerciser tool (7558) tobattery positive terminal. Connect the black clip tonegative battery terminal. The red lamp on the exer-ciser tool will be illuminated when the exerciser isproperly connected to battery.

(4) Start engine.When the switch is in the HIGH or LOW position,

the lamp on the exerciser tool will flash. This indi-cates that voltage pulses are being sent to the IACstepper motor.

(5) Move the switch to the HIGH position. The en-gine speed should increase. Move the switch to theLOW position. The engine speed should decrease.

(a) If the engine speed changes while using theexerciser tool, the IAC motor is functioning prop-erly. Disconnect the exerciser tool and connect theIAC stepper motor wire connector to the steppermotor.

(b) If the engine speed does not change, turn theignition OFF and proceed to step (6). Do not dis-connect exerciser from the IAC stepper motor.(6) Remove the IAC stepper motor from the throt-

tle body.


Fig. 25 IAC Motor Testing—Typical


CAUTION: When checking IAC motor operation withthe motor removed from the throttle body, do notextend the pintle (Fig. 26) more than 6.35 mm (.250in). If the pintle is extended more than this amount, itmay separate from the IAC stepper motor. The IAC mo-tor must be replaced if the pintle separates from themotor.

(7) With the ignition OFF, cycle the exerciser toolswitch between the HIGH and LOW positions. Ob-serve the pintle. The pintle should move in-and-outof the motor.

(a) If the pintle does not move, replace the IACmotor. Start the engine and test the replacementmotor operation as described in step (5).

(b) If the pintle operates properly, check the IACmotor bore in the throttle body bore for blockageand clean as necessary. Install the IAC motor andretest. If blockage is not found, refer to the DRBscan tool and the appropriate Powertrain Diagnos-tics Procedures service manual.

RELAYS—OPERATION/TESTING

OPERATIONThe following operations/tests apply to these

relays only: automatic shutdown (ASD) and fuelpump. For operations/tests on all other relays, referto the appropriate section of this service manual.

These relays are located in the power distributioncenter (PDC) (Fig. 27). For the location of the relaywithin the PDC, refer to label under PDC cover.

The relay terminal numbers from (Fig. 28) can befound on the bottom of the relay.• Terminal number 30 is connected to battery volt-age and can be switched or B+ (hot) at all times.• The center terminal number 87A is connected (acircuit is formed) to terminal 30 in the de-energized(normally OFF) position.• Terminal number 87 is connected (a circuit isformed) to terminal 30 in the energized (ON) posi-

tion. Terminal number 87 then supplies battery volt-age to the component being operated.• Terminal number 86 is connected to a switched (+)power source.• Terminal number 85 is grounded by the power-train control module (PCM).

TESTING(1) Remove relay before testing.(2) Using an ohmmeter, perform a resistance test

between terminals 85 and 86. Resistance value(ohms) should be 75 65 ohms for resistor equippedrelays.

(3) Connect the ohmmeter between terminals num-ber 87A and 30. Continuity should be present at thistime.

(4) Connect the ohmmeter between terminals num-ber 87 and 30. Continuity should not be present atthis time.

(5) Use a set of jumper wires (16 gauge or small-er). Connect one jumper wire between terminal num-ber 85 (on the relay) to the ground side (-) of a 12Volt power source.

(6) Attach the other jumper wire to the positiveside (+) of a 12V power source. Do not connect thisjumper wire to relay at this time.

CAUTION: Do not allow the ohmmeter to contactterminals 85 or 86 during these tests. Damage toohmmeter may result.

(7) Attach the other jumper wire (12V +) to termi-nal number 86. This will activate the relay. Continu-ity should now be present between terminals number87 and 30. Continuity should not be present between

Fig. 26 IAC Stepper Motor Pintle—Typical



terminals number 87A and 30.(8) Disconnect jumper wires from relay and 12 Volt

power source.If continuity or resistance tests did not pass, re-

place relay. If tests passed, refer to Group 8W, WiringDiagrams for wiring schematics and for additionalcircuit information.

STARTER MOTOR RELAY TESTRefer to Group 8A, Battery/Starting/Charging Sys-

tem Diagnostics, for starter motor relay testing.

FUEL INJECTOR TESTDisconnect the fuel injector wire harness connector

from the injector (Fig. 29). Place an ohmmeter acrossthe injector terminals. Resistance reading should beapproximately 14.5 ohms 61.2 ohms at 20°C (68°F).Proceed to following Fuel Injector diagnosis chart.When performing the following tests from thechart, do not leave electrical current applied tothe injector for longer than five seconds. Dam-age to injector coil or internal injector sealscould result.

FUEL PUMP PRESSURE TESTRefer to Fuel Pump Pressure Test in the Fuel De-

livery System section of this group.

ON-BOARD DIAGNOSTICS (OBD)The powertrain control module (PCM) has been

programmed to monitor many different circuits of thefuel injection system. If a problem is sensed in amonitored circuit often enough to indicate an actual

Fig. 28 Relay Terminals

Fig. 29 Fuel Injector Wiring Connector—Typical


problem, a Diagnostic Trouble Code (DTC) is stored.The DTC will be stored in the PCM memory for even-tual display to the service technician. If the problemis repaired or ceases to exist, the PCM cancels theDTC after 51 engine starts.

Certain criteria must be met for a diagnostic trou-ble code (DTC) to be entered into PCM memory. Thecriteria may be a specific range of engine rpm, enginetemperature and/or input voltage to the PCM.

It is possible that a DTC for a monitored circuitmay not be entered into memory even though a mal-function has occurred. This may happen because oneof the DTC criteria for the circuit has not been met.Example: assume that one of the criteria for theMAP sensor circuit is that the engine must be oper-ating between 750 and 2000 rpm to be monitored fora DTC. If the MAP sensor output circuit shorts toground when the engine rpm is above 2400 rpm, a 0volt input will be seen by the PCM. A DTC will notbe entered into memory because the condition doesnot occur within the specified rpm range.

A DTC indicates that the powertrain control mod-ule (PCM) has recognized an abnormal signal in acircuit or the system. A DTC may indicate the resultof a failure, but never identify the failed componentdirectly.

There are several operating conditions that thePCM does not monitor and set a DTC for. Refer tothe following Monitored Circuits and Non-MonitoredCircuits in this section.

MONITORED CIRCUITSThe powertrain control module (PCM) can detect

certain problems in the fuel injection system.Open or Shorted Circuit - The PCM can deter-

mine if sensor output (which is the input to PCM) iswithin proper range. It also determines if the circuitis open or shorted.

Output Device Current Flow - The PCM senseswhether the output devices are hooked up.

If there is a problem with the circuit, the PCMsenses whether the circuit is open, shorted to ground(-), or shorted to (+) voltage.

Oxygen Sensor - The PCM can determine if theoxygen sensor is switching between rich and lean.This is, once the system has entered Closed Loop. Re-fer to Open Loop/Closed Loop Modes Of Operation inthe Component Description/System Operation sectionfor an explanation of Closed (or Open) Loop opera-tion.

NON-MONITORED CIRCUITSThe PCM does not monitor the following circuits,

systems or conditions that could have malfunctionsthat result in driveability problems. A DiagnosticTrouble Code (DTC) may not be displayed for theseconditions.

Fuel Pressure: Fuel pressure is controlled by thefuel pressure regulator. The PCM cannot detect aclogged fuel pump inlet filter, clogged in-line fuel fil-ter, or a pinched fuel supply line. However, thesecould result in a rich or lean condition causing an ox-ygen sensor DTC to be stored in the PCM.

Secondary Ignition Circuit: The PCM cannotdetect an inoperative ignition coil, fouled or wornspark plugs, ignition cross firing, or open circuitedspark plug cables.

Engine Timing: The PCM cannot detect an incor-rectly indexed timing chain, camshaft sprocket orcrankshaft sprocket. The PCM also cannot detect anincorrectly indexed distributor. However, these couldresult in a rich or lean condition causing an oxygensensor DTC to be stored in the PCM.

Cylinder Compression: The PCM cannot detectuneven, low, or high engine cylinder compression.

Exhaust System: The PCM cannot detect aplugged, restricted or leaking exhaust system.

Fuel Injector Malfunctions: The PCM cannot de-termine if the fuel injector is clogged, or the wronginjector is installed. However, these could result in arich or lean condition causing an oxygen sensor DTCto be stored in the PCM.

Excessive Oil Consumption: Although the PCMmonitors exhaust stream oxygen content through ox-ygen sensor (closed loop), it cannot determine exces-sive oil consumption.

Throttle Body Air Flow: The PCM cannot detecta clogged or restricted air cleaner inlet or air cleanerelement.

Evaporative System: The PCM will not detect arestricted, plugged or loaded EVAP canister.

Vacuum Assist: Leaks or restrictions in the vac-uum circuits of vacuum assisted engine control sys-tem devices are not monitored by the PCM. However,a vacuum leak at the MAP sensor will be monitoredand a diagnostic trouble code (DTC) will be gener-ated by the PCM.

Fig. 30 Fuel Injector Internal Components—Typical


INJECTOR DIAGNOSIS—VEHICLE RUNS ROUGH AND/OR HAS A MISS


Powertrain Control Module (PCM) SystemGround: The PCM cannot determine a poor systemground. However, a DTC may be generated as a re-sult of this condition.

Powertrain Control Module (PCM) ConnectorEngagement: The PCM cannot determine spread ordamaged connector pins. However, a DTC may begenerated as a result of this condition.

HIGH AND LOW LIMITSThe powertrain control module (PCM) compares in-

put signal voltages from each input device. It will es-tablish high and low limits that are programmed intoit for that device. If the input voltage is not withinspecifications and other Diagnostic Trouble Code(DTC) criteria are met, a DTC will be stored in mem-ory. Other DTC criteria might include engine rpmlimits or input voltages from other sensors orswitches. The other inputs might have to be sensedby the PCM when it senses a high or low input volt-age from the control system device in question.

ACCESSING DIAGNOSTIC TROUBLE CODESA stored Diagnostic Trouble Code (DTC) can be dis-

played by cycling the ignition key On-Off-On-Off-Onwithin three seconds and observing the malfunctionindicator lamp. This lamp is displayed on the instru-ment panel as the CHECK ENGINE lamp (Fig. 31).

They can also be displayed through the use of theDiagnostic Readout Box (DRB scan tool). The DRBconnects to the data link connector in the vehicle(Fig. 32). For operation of the DRB, refer to the ap-propriate Powertrain Diagnostic Procedures servicemanual.

EXAMPLES:• If the lamp (Fig. 31) flashes 1 time, pauses andflashes 2 more times, a flashing Diagnostic TroubleCode (DTC) number 12 is indicated. If this code isobserved, it is indicating that the battery has beendisconnected within the last 50 key-on cycles. It

could also indicate that battery voltage has been dis-connected to the PCM. In either case, other DTC’smay have been erased.• If the lamp flashes 3 times, pauses and flashes 1more time, a Diagnostic Trouble Code (DTC) number31 is indicated.• If the lamp flashes 1 time, pauses and flashes 4more times, a Diagnostic Trouble Code (DTC) num-ber 14 is indicated.

After any stored DTC information has been ob-served, the display will end with a flashing DTCnumber 55. This will indicate the end of all stored in-formation.

Refer to the Diagnostic Trouble Code (DTC) chartsfor DTC identification.

If the problem is repaired or ceases to exist, thepowertrain control module (PCM) cancels the DTCafter 51 engine starts.

Diagnostic Trouble Codes indicate the results of afailure, but never identify the failed component di-rectly.

The circuits of the data link connector are shown in(Fig. 33).

ERASING TROUBLE CODESUse the DRB scan tool to erase a Diagnostic Trou-

ble Code (DTC). Refer to the appropriate PowertrainDiagnostic Procedures service manual for operationof the DRB scan tool.

DRB SCAN TOOLFor operation of the DRB scan tool, refer to the ap-

propriate Powertrain Diagnostic Procedures servicemanual.




DIAGNOSTIC TROUBLE CODE (DTC)On the following pages, a list of diagnostic trouble

codes is provided for the 5.2L V-8 engine. A DTC in-

dicates that the powertrain control module (PCM)has recognized an abnormal signal in a circuit or thesystem. A DTC may indicate the result of a failure,but never identify the failed component directly.

DIAGNOSTIC TROUBLE CODE DESCRIPTIONSDiagnostic


11* No Crank Reference Signal at PCM No crank reference signal detected during en-gine cranking.

12* Battery Disconnect Direct battery input to PCM was disconnectedwithin the last 50 Key-on cycles.

13** No Change in MAP From Start to Run No difference recognized between the engineMAP reading and the barometric (atmospheric)pressure reading at start-up.

14** MAP Sensor Voltage Too Low MAP sensor input below minimum acceptablevoltage.

or

MAP Sensor Voltage Too High MAP sensor input above maximum acceptablevoltage.

15** No Vehicle Speed Sensor Signal No vehicle distance (speed) sensor signal de-tected during road load conditions.

17* Engine is Cold Too Long Engine coolant temperature remains belownormal operating temperatures during vehicletravel (thermostat).

21** O2S Stays at Center Neither rich or lean condition detected fromthe oxygen sensor input.

or

O2S Shorted to Voltage Oxygen sensor input voltage maintained abovethe normal operating range.



Fig. 33 Data Link Connector Schematic


DIAGNOSTIC TROUBLE CODE DESCRIPTIONS—CONTINUEDDiagnostic


22** ECT Sensor Voltage Too High Engine coolant temperature sensor inputabove maximum acceptable voltage.

or

ECT Sensor Voltage Too Low Engine coolant temperature sensor input belowminimum acceptable voltage.

23** Intake Air Temp Sensor Voltage Low Intake manifold air temperature sensor inputbelow the minimum acceptable voltage.

or

Intake Air Temp Sensor Voltage High Intake manifold air temperature sensor inputabove the maximum acceptable voltage.

24** Throttle Position Sensor Voltage High Throttle position sensor input above the maxi-mum acceptable voltage.

or

Throttle Position Sensor Voltage Low Throttle position sensor input below the mini-mum acceptable voltage.

25** Idle Air Control Motor Circuits A shorted condition detected in one or more ofthe idle air control motor circuits.

27* Injector #1 Control Circuit Injector #1 output driver does not respondproperly to the control signal.

or


or


or


or


or


or







or


31** EVAP Solenoid Circuit An open or shorted condition detected in theEVAP solenoid circuit.

32** EGR Solenoid Circuit An open or shorted condition detected in theEGR solenoid circuit.

or

EGR System Failure A mechanical problem found in EGR system(vacuum line leak, defective EGR valve,plugged EGR tube, etc.).

33* A/C Clutch Relay Circuit An open or shorted condition detected in theA/C clutch relay circuit.

34* Speed Control Solenoid Circuits An open or shorted condition detected in theSpeed Control vacuum or vent solenoid cir-cuits.

or

Speed Control Switch Always Low Speed Control switch input below the mini-mum acceptable voltage.

or

Speed Control Switch Always High Speed Control switch input above the maxi-mum acceptable voltage.

41** Generator Field Not Switching Properly An open or shorted condition detected in thegenerator field control circuit.

42* Auto Shutdown Relay Control Circuit An open or shorted condition detected in theauto shutdown relay circuit.

44* Battery Temp Sensor Volts out of Limit An open or shorted condition exists in the en-gine coolant temperature sensor circuit or aproblem exists in the PCM’s battery tempera-ture voltage circuit.

46** Charging System Voltage Too High Battery voltage sense input above targetcharging voltage during engine operation.

47** Charging System Voltage Too Low Battery voltage sense input below targetcharging during engine operation. Also, no sig-nificant change detected in battery voltageduring active test of generator output.






51** O2S Signal Stays Below Center (Lean) Oxygen sensor signal input indicates lean air/fuel ratio condition during engine operation.

52** O2S Signal Stays Above Center (Rich) Oxygen sensor signal input indicates rich air/fuel ratio condition during engine operation.

53* Internal PCM Failure PCM Internal fault condition detected.

or

PCM Failure SPI (Serial Peripheral Inter-face) Communications

PCM Internal fault condition detected.

54* No Cam Sync Signal at PCM No fuel sync (camshaft signal) detected duringengine cranking.

55* Display not shown on DRB scan tool Completion of diagnostic trouble code displayon the Malfunction Indicator Lamp (Check En-gine Lamp).

62* PCM Failure SRI miles not stored Unsuccessful attempt to update SRI (servicereminder indicator) miles in the PCM EE-PROM.

63* PCM Failure EEPROM Write Denied Unsuccessful attempt to write to an EEPROMlocation by the PCM.




MULTI-PORT FUEL INJECTION (MFI)—5.2L V-8 ENGINE—COMPONENTREMOVAL/INSTALLATION

INDEX

page page

Accelerator Pedal and Throttle Cable . . . . . . . . . . . 86Air Cleaner Element . . . . . . . . . . . . . . . . . . . . . . . 85Air Cleaner Housing . . . . . . . . . . . . . . . . . . . . . . . 85Air Conditioning (A/C) Clutch Relay . . . . . . . . . . . . 86Automatic Shutdown (ASD) Relay . . . . . . . . . . . . . 86Brake Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86Camshaft Position Sensor . . . . . . . . . . . . . . . . . . . 86Crankshaft Position Sensor . . . . . . . . . . . . . . . . . . 87Engine Coolant Temperature Sensor . . . . . . . . . . . 87Evap Canister Purge Solenoid . . . . . . . . . . . . . . . . 87Fuel Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87Fuel Injector(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . 87Fuel Pressure Regulator . . . . . . . . . . . . . . . . . . . . 88Fuel Pump Module . . . . . . . . . . . . . . . . . . . . . . . . 88Fuel Pump Relay . . . . . . . . . . . . . . . . . . . . . . . . . 88Fuel Rail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Fuel System Pressure Release Procedure . . . . . . . 90Fuel Tank Pressure Relief/Rollover Valve . . . . . . . . 90Fuel Tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Fuel Tubes/Lines/Hoses and Clamps . . . . . . . . . . . 90Idle Air Control (IAC) Motor . . . . . . . . . . . . . . . . . . 90Ignition Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Intake Manifold . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Intake Manifold Air Temperature Sensor . . . . . . . . . 86Manifold Absolute Pressure (MAP) Sensor . . . . . . . 90Oxygen (O2S) Sensor . . . . . . . . . . . . . . . . . . . . . . 91Park/Neutral Switch . . . . . . . . . . . . . . . . . . . . . . . . 91Powertrain Control Module (PCM) . . . . . . . . . . . . . 91Quick-Connect Fittings . . . . . . . . . . . . . . . . . . . . . 92Throttle Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92Throttle Position Sensor (TPS) . . . . . . . . . . . . . . . 93Vehicle Speed Sensor . . . . . . . . . . . . . . . . . . . . . . 93

AIR CLEANER HOUSING

REMOVAL(1) Unlock clean air hose clamp (Fig. 1) at air

cleaner cover. To unlock the clamp, attach adjustablepliers to clamp and rotate pliers as shown in figure2. Remove clean air hose at cover.

(2) Remove crankcase breather/filter hose at aircleaner cover.

(3) From under vehicle, remove three housing nuts(Fig. 1).

(4) Release the air cleaner housing from the ambi-ent air duct and remove housing from vehicle.

INSTALLATION(1) Position air cleaner housing to body and ambi-

ent air duct (Fig. 1).(2) Install three nuts and tighten to 10 Nzm (93 in.

lbs.) torque.(3) Install crankcase breather/filter hose to cover.(4) Install clamp to cover. Compress the clamp

snugly with adjustable pliers as shown in figure 3.

AIR CLEANER ELEMENT

REMOVAL/INSTALLATION(1) Pry back the six clips retaining the air cleaner

cover to the air cleaner housing (Fig. 4).

Fig. 1 Air Cleaner—5.2L V-8 Engine

Fig. 2 Clamp Removal

ZJ FUEL SYSTEM COMPONENT REMOVAL/INSTALLATION—5.2L V-8 ENGINE 14 - 85

(2) Lift the cover up and position to the side.(3) Remove air cleaner element.(4) Clean the inside of air cleaner housing before

installing new element.(5) Reverse the preceding operation for installa-

tion. Be sure the air cleaner cover is properly seatedto air cleaner housing.

ACCELERATOR PEDAL AND THROTTLE CABLERefer to the Accelerator Pedal and Throttle Cable

section of this group for removal/installation proce-dures.

AIR CONDITIONING (A/C) CLUTCH RELAYThe A/C clutch relay is located in the power distri-


AUTOMATIC SHUTDOWN (ASD) RELAYThe ASD relay is located in the power distribution

center (Fig. 5) (PDC). For location of this relaywithin the PDC, refer to label attached to bottom ofPDC cover.

BRAKE SWITCHRefer to Group 5, Brakes for removal/installation

procedures.

CAMSHAFT POSITION SENSORFor removal/installation procedures, refer to Group

8D, Ignition System. See Camshaft Position Sensor.

INTAKE MANIFOLD AIR TEMPERATURE SENSORThe intake manifold air temperature sensor is lo-

cated in the front/side of the intake manifold (Fig. 6).

REMOVAL(1) Remove air cleaner assembly.(2) Disconnect electrical connector at sensor (Fig.

6).(3) Remove sensor from intake manifold.

INSTALLATION(1) Install sensor to intake manifold. Tighten to 28

Nzm (20 ft. lbs.) torque.(2) Install electrical connector.(3) Install air cleaner.

Fig. 3 Clamp Installation

Fig. 4 Typical Air Cleaner Element Removal/Installation


14 - 86 FUEL SYSTEM COMPONENT REMOVAL/INSTALLATION—5.2L V-8 ENGINE ZJ

CRANKSHAFT POSITION SENSORFor removal and installation procedures, refer to

Group 8D, Ignition System.

ENGINE COOLANT TEMPERATURE SENSOR

REMOVAL

WARNING: HOT, PRESSURIZED COOLANT CANCAUSE INJURY BY SCALDING. COOLING SYSTEMMUST BE PARTIALLY DRAINED BEFORE REMOV-ING THE COOLANT TEMPERATURE SENSOR. RE-FER TO GROUP 7, COOLING.

(1) Partially drain cooling system. Refer to Group7, Cooling.

(2) Disconnect electrical connector from sensor(Fig. 7).

Engines with air conditioning: When removingthe connector from sensor, do not pull directly on wir-ing harness. Fabricate an L-shaped hook tool from acoat hanger (approximately eight inches long). Placethe hook part of tool under the connector for removal.The connector is snapped onto the sensor. It is notequipped with a lock type tab.

(3) Remove sensor from intake manifold.

INSTALLATION(1) Install sensor.(2) Tighten to 11 Nzm (8 ft. lbs.) torque.(3) Connect electrical connector to sensor.The sensor connector is symmetrical (not indexed).

It can be installed to the sensor in either direction.(4) Replace any lost engine coolant. Refer to Group

7, Cooling System.

EVAP CANISTER PURGE SOLENOIDRefer to Group 25, Emission Control System for re-


FUEL FILTERRefer to the Fuel Delivery System section of this


FUEL INJECTOR(S)

WARNING: THE FUEL SYSTEM IS UNDER A CON-STANT PRESSURE EVEN WITH THE ENGINETURNED OFF. BEFORE SERVICING THE FUEL IN-JECTOR(S), THE FUEL SYSTEM PRESSURE MUSTBE RELEASED.

To release fuel pressure, refer to the Fuel DeliverySystem section of this group. See Fuel System Pres-sure Release Procedure.

To remove one or more fuel injectors, the fuel railassembly must be removed from engine.

REMOVAL(1) Remove air duct at throttle body.(2) Remove fuel rail assembly. Refer to Fuel Rail

removal in this section.(3) Remove the clip(s) retaining the injector(s) to

fuel rail (Figs. 8 or 9).

Fig. 6 Air Temperature Sensor—Typical Fig. 7 Coolant Temperature Sensor—Typical

Fig. 8 Injector Mounting


(4) Remove injector(s) from fuel rail.

INSTALLATION(1) Apply a small amount of clean engine oil to

each fuel injector o-ring. This will help in fuel rail in-stallation.

(2) Install injector(s) and injector clip(s) to fuelrail.

(3) Install fuel rail assembly. Refer to Fuel Rail in-stallation.

(4) Install air duct to throttle body.(5) Start engine and check for leaks.

FUEL PRESSURE REGULATORThe fuel pressure regulator is part of the fuel

pump module and is not serviced separately. If itneeds replacement, the fuel pump module assemblymust be replaced. See Fuel Pump Module in the FuelDelivery section of this group for procedures.

FUEL PUMP MODULERefer to the Fuel Delivery System section of this


FUEL PUMP RELAYThe fuel pump relay is located in the power distri-


FUEL RAIL

WARNING: THE FUEL SYSTEM IS UNDER A CON-STANT PRESSURE EVEN WITH THE ENGINE

TURNED OFF. BEFORE SERVICING THE FUEL RAILASSEMBLY, THE FUEL SYSTEM PRESSURE MUSTBE RELEASED.


CAUTION: The left and right fuel rails are replacedas an assembly. Do not attempt to separate the railhalves at the connecting hose (Fig. 10). Due to thedesign of this connecting hose, it does not use anyclamps. Never attempt to install a clamping deviceof any kind to the hose. When removing the fuel railassembly for any reason, be careful not to bend orkink the connecting hose.

REMOVAL(1) Remove negative battery cable at battery.(2) Remove air duct at throttle body.(3) Perform the fuel system pressure release proce-

dure. Refer to the Fuel Delivery System section ofthis group.

(4) Remove throttle body from intake manifold. Re-fer to Throttle Body removal in this group.

(5) If equipped with air conditioning, remove theA/C compressor-to-intake manifold support bracket(three bolts) (Fig. 11).

(6) Disconnect electrical connectors at all fuel in-jectors (Fig. 12). The factory fuel injection wiring har-ness is numerically tagged (INJ 1, INJ 2, etc.) forinjector position identification.

(7) Remove EVAP canister purge solenoid/bracketassembly (Fig. 13) from intake manifold.

(8) Disconnect the fuel supply line at the fuel rail.For procedures, refer to Fuel Tubes/Lines/Hoses andClamps, or Quick-Connect Fittings in the Fuel Deliv-ery System section of this group.

(9) Remove the remaining fuel rail mounting bolts(Fig. 10).

Fig. 9 Injector Retaining Clips—Typical Injector

Fig. 10 Fuel Rail Assembly—Typical


(10) Gently rock and pull the left fuel rail untilthe fuel injectors just start to clear the intake mani-fold. Gently rock and pull the right fuel rail untilthe fuel injectors just start to clear the intake mani-fold. Repeat this procedure (left/right) until all fuelinjectors have cleared the intake manifold.

(11) Remove fuel rail (with injectors attached) fromengine.

(12) Remove the clip(s) retaining the injector(s) tofuel rail (Fig. 14).

INSTALLATION(1) Apply a small amount of engine oil to each fuel

injector o-ring. This will help in fuel rail installation.(2) Install injector(s) and injector clip(s) to fuel

rail.

(3) Position the fuel rail/fuel injector assembly tothe injector openings on the intake manifold.

(4) Guide each injector into the intake manifold.Be careful not to tear the injector o-ring.

(5) Push the right fuel rail down until fuel injec-tors have bottomed on injector shoulder. Push theleft fuel rail down until fuel injectors have bottomedon injector shoulder.

(6) Install fuel rail mounting bolts.(7) Install EVAP canister purge solenoid to intake

manifold.(8) Connect electrical connector to intake manifold

air temperature sensor.(9) Connect wiring to all fuel injectors. The injector

wiring harness is numerically tagged.(10) Install the A/C support bracket (if equipped).(11) Install throttle body to intake manifold. Refer

to Throttle Body installation in this section of thegroup.

(12) Install fuel supply line to fuel rail. Refer toFuel Tubes/Lines/Hoses and Clamps, or Quick-Con-nect Fittings in the Fuel Delivery System section ofthis group.

Fig. 11 A/C Compressor Support Bracket—Typical

Fig. 12 Fuel Injector Connectors—Typical

Fig. 13 EVAP Canister Purge Solenoid

Fig. 14 Fuel Injector Clip


(13) Install air duct at throttle body.(14) Connect battery cable to battery.(15) Start engine and check for leaks.


WARNING: THE FUEL SYSTEM IS UNDER A CON-STANT PRESSURE EVEN WITH THE ENGINETURNED OFF. BEFORE SERVICING THE FUELPUMP, FUEL LINES, FUEL FILTER, OR FUEL INJEC-TOR(S), THE FUEL SYSTEM PRESSURE MUST BERELEASED.


FUEL TANKSRefer to the Fuel Tank section of this group for re-


FUEL TANK PRESSURE RELIEF/ROLLOVER VALVERefer to the Fuel Tank section of this group for re-


FUEL TUBES/LINES/HOSES AND CLAMPSRefer to Fuel Tubes/Lines/Hoses and Clamps in the

Fuel Delivery System section of this group for remov-al/installation procedures.

Also refer to Quick-Connect Fittings in the FuelDelivery System section of this group for removal/in-stallation procedures.

IDLE AIR CONTROL (IAC) MOTORThe IAC motor is located on the back of the throt-

tle body (Fig. 15).

REMOVAL(1) Remove air duct at throttle body.(2) Disconnect electrical connector from IAC motor.(3) Remove two mounting bolts (Fig. 16).(4) Remove IAC motor from throttle body.

INSTALLATION(1) Install IAC motor to throttle body.(2) Install and tighten two mounting bolts to 7

Nzm (60 in. lbs.) torque.(3) Install electrical connector.(4) Install air duct to throttle body.

IGNITION COILRefer to Group 8D, Ignition Systems for removal/

installation procedures.

INTAKE MANIFOLDRefer to Group 11, Exhaust System and Intake

Manifold for removal/installation procedures.

MANIFOLD ABSOLUTE PRESSURE (MAP) SENSORThe MAP sensor is located on the front of the

throttle body (Fig. 17). An L-shaped rubber fitting isused to connect the MAP sensor to throttle body (Fig.18).

REMOVALThe throttle body must be removed from the intake

manifold for MAP sensor removal.(1) Remove air duct at throttle body.(2) Remove throttle body. Refer to Throttle Body

removal in this section.(3) Remove two MAP sensor mounting bolts (Fig.

18).

Fig. 15 Idle Air Control Motor and MAP Sensor

Fig. 16 Mounting Bolts—IAC Motor


(4) While removing MAP sensor, slide the vacuumrubber L-shaped fitting (Fig. 18) from the throttlebody.

(5) Remove rubber L-shaped fitting from MAP sen-sor.

INSTALLATION(1) Install rubber L-shaped fitting to MAP sensor.(2) Position sensor to throttle body while guiding

rubber fitting over throttle body vacuum nipple.(3) Install MAP sensor mounting bolts. Tighten

screws to 3 Nzm (25 in. lbs.) torque.(4) Install throttle body. Refer to Throttle Body in-

stallation in this section.(5) Install air duct to throttle body.

OXYGEN (O2S) SENSORThe O2S sensor is located in the right exhaust

down-pipe below the exhaust manifold flange (Fig.18).

REMOVAL

WARNING: THE EXHAUST MANIFOLD BECOMESVERY HOT DURING ENGINE OPERATION. ALLOWENGINE TO COOL BEFORE REMOVING OXYGENSENSOR.

(1) Raise and support the vehicle.(2) Disconnect the wire connector from the O2S

sensor.

CAUTION: When disconnecting the sensor electricalconnector, do not pull directly on wire going intosensor.

(3) Remove the O2S sensor from the exhaust man-ifold. Snap-On oxygen sensor wrench (number YA8875) may be used for removal and installation.

INSTALLATIONThreads of new oxygen sensors are factory coated

with anti-seize compound to aid in removal. DONOT add any additional anti-seize compound tothe threads of a new oxygen sensor.

(1) Install the O2S sensor into the exhaust mani-fold. Tighten to 30 Nzm (22 ft. lbs.) torque.

(2) Connect the O2S sensor wire connector.(3) Lower the vehicle.

PARK/NEUTRAL SWITCHRefer to Group 21, Transmission and Transfer Case

for removal/installation procedures.

POWERTRAIN CONTROL MODULE (PCM)The PCM is located on the cowl panel in the right/

rear side of the engine compartment (Fig. 19).

REMOVAL(1) Disconnect the negative battery cable at the

battery.(2) Remove the coolant reserve/overflow tank (one

bolt and two nuts) (Fig. 20)(3) Loosen the 60-Way connector mounting bolt

(Fig. 21).(4) Remove the electrical connector by pulling

straight back.(5) Remove the three PCM mounting bolts (Fig.

21).(6) Remove PCM.

INSTALLATION(1) Check the pins in 60-way electrical connector

for damage. Repair as necessary.(2) Install PCM. Tighten three mounting bolts to 1

Nzm (9 in. lbs.) torque.(3) Engage 60-way connector into PCM. Tighten

connector mounting bolt to 4 Nzm (35 in. lbs.) torque.(4) Install coolant reserve/overflow tank.(5) Connect negative cable to battery.

Fig. 17 MAP Sensor L-Shaped Rubber Fitting

Fig. 18 Oxygen Sensor


QUICK-CONNECT FITTINGSRefer to the Fuel Delivery System section of this


THROTTLE BODYA (factory adjusted) set screw is used to mechani-

cally limit the position of the throttle body throttleplate. Never attempt to adjust the engine idlespeed using this screw. All idle speed functions arecontrolled by the powertrain control module (PCM).

REMOVAL(1) Remove the air duct at throttle body.(2) Disconnect throttle body electrical connectors at

MAP sensor, IAC motor and TPS (Fig. 22).

(3) Remove vacuum line at throttle body.(4) Remove (unsnap) all control cables from throt-

tle body (lever) arm. Refer to the Accelerator Pedaland Throttle Cable section of this group for addi-tional information.

Fig. 19 Powertrain Control Module (PCM) Location

Fig. 20 Coolant Reserve/Overflow Tank Mounting

Fig. 21 Powertrain Control Module (PCM) Mounting

Fig. 22 Throttle Body and TPS—Typical


(5) Remove four throttle body mounting bolts (Fig.23).

(6) Remove throttle body from intake manifold.(7) Discard old throttle body-to-intake manifold

gasket.

INSTALLATION(1) Clean the mating surfaces of the throttle body

and the intake manifold.(2) Install new throttle body-to-intake manifold

gasket.(3) Install throttle body to intake manifold.(4) Install four mounting bolts. Tighten bolts to 23

Nzm (200 in. lbs.) torque.(5) Install control cables.

CAUTION: When the automatic transmission throttlecable is connected, it MUST be adjusted.

(6) If equipped with an automatic transmission,connect and adjust the transmission line pressure ca-ble. Refer to Group 21, Transmissions for adjustmentprocedure.

(7) Install vacuum line to throttle body.(8) Install electrical connectors.(9) Install air duct to throttle body.

THROTTLE POSITION SENSOR (TPS)

REMOVALThe TPS is located on the side of the throttle body

(Fig. 22).(1) Remove air intake tube at throttle body.(2) Disconnect TPS electrical connector.

(3) Remove two TPS mounting bolts (Fig. 24).

(4) Remove TPS from throttle body.

INSTALLATIONThe throttle shaft end of the throttle body slides

into a socket in the TPS (Fig. 25). The TPS must beinstalled so that it can be rotated a few degrees. Ifthe sensor will not rotate, install the sensor with thethrottle shaft on the other side of the socket tangs.The TPS will be under slight tension when rotated.

(1) Install the TPS and two retaining bolts.(2) Tighten bolts to 7 Nzm (60 in. lbs.) torque.(3) Manually operate the throttle control lever by

hand to check for any binding of the TPS.(4) Connect TPS electrical connector to TPS.(5) Install air intake tube.

VEHICLE SPEED SENSORThe vehicle speed sensor (Fig. 26) is located on the

extension housing of the transmission on 2WD mod-els. It is located on the transfer case on 4WD models.

Fig. 23 Throttle Body Mounting Bolts—Typical

Fig. 24 TPS Mounting Bolts

Fig. 25 TPS Installation


REMOVAL

(1) Raise and support vehicle.(2) Disconnect the electrical connector from the

sensor.(3) Remove the sensor mounting bolt (Fig. 27).(4) Remove the sensor (pull straight out) from the

speedometer pinion gear adapter (Fig. 27). Do not re-move the gear adapter from the transmission.

INSTALLATION(1) Clean the inside of speedometer pinion gear

adapter before installing speed sensor.(2) Install sensor into speedometer gear adapter

and install mounting bolt. Before tightening bolt,verify speed sensor is fully seated (mountedflush) to speedometer pinion gear adapter.

(3) Tighten sensor mounting bolt to 2.2 Nzm (20 in.lbs.) torque.

(4) Connect electrical connector to sensor.

Fig. 26 Vehicle Speed Sensor Location—Typical

Fig. 27 Sensor Removal/Installation—Typical


SPECIFICATIONS

GENERAL INFORMATIONThe following specifications are published from the

latest information available at the time of publica-tion. If anything differs between the specifica-tions found on the Vehicle Emission ControlInformation (VECI) label and the followingspecifications, use specifications on VECI label.The VECI label is located in the engine compart-ment.

FUEL SYSTEM PRESSUREThe fuel system operating pressure for either 4.0L

6-cylinder or 5.2L V-8 engines is 255-283 kPa (39 psi6 2 psi). This is measured at the fuel rail test port.Pump output pressure at the fuel pump module out-let fitting is 269-283 kPa (39-41 psi).

FUEL TANK CAPACITIES

TORQUE

ZJ FUEL SYSTEM SPECIFICATIONS 14 - 95

Automotive

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