A i r S p r i n g A i r Tu b e s a n d F i t t i n g s N O ... · Trim Height Test (or Accurate Trim Test) Self-Test Vehicle Dynamics Module (VDM) DTC Chart Symptom Chart Pinpoint

7/21/2017 Vehicle Dynamic Suspension - Diagnosis and Testing • 2008 Ford Expedition • MotoLogic

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2008 Expedition

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Principles of OperationInspection and VerificationPneumatic TestTrim Height Test (or Accurate Trim Test)Self-TestVehicle Dynamics Module (VDM) DTC ChartSymptom ChartPinpoint TestsComponent TestRelay

SECTION 204-05: Vehicle Dynamic Suspension 2008 Expedition/Navigator Workshop Manual

DIAGNOSIS AND TESTING Procedure revision date: 10/04/2010

Vehicle Dynamic Suspension

Special Tool(s)

73 Digital Multimeter or equivalent 105-R0051 or equivalent

Flex Probe Kit 105-R025B or equivalent

Vacuum Tester or equivalent 014-R1054

Vehicle Communication Module (VCM) and Integrated Diagnostic System (IDS) software withappropriate hardware, or equivalent scan tool

Principles of Operation

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WARNING: Shut off the electrical power to the air suspension system prior to hoisting or jacking an airsuspension equipped vehicle. Failure to do so may result in unexpected inflation or deflation of the airsprings, which may result in shifting of the vehicle during these operations. Failure to follow thisinstruction may result in serious personal injury.

WARNING: Vent all air pressure from the air suspension system prior to disconnecting or removing anyair suspension components. It is dangerous to remove air suspension components while underpressure. Failure to follow this instruction may result in serious personal injury.

WARNING: Always inflate air springs before loading the suspension. If a load is applied to an uninflatedair spring, the spring may be damaged and a new air spring will have to be installed. Damaged springsdegrade vehicle handling, which could result in serious injury to vehicle occupant(s).

WARNING: Inspect the air spring for correct shape after it has been inflated with the wheels off theground and the suspension unloaded. A deformed air spring could fail. Failure to follow this instructionmay result in serious injury to the technician or vehicle occupant(s).

The air suspension system is designed to improve ride handling and general vehicle driving performance. Amicroprocessor controls the air suspension system. The microprocessor and the supporting hardware arecontained in the Vehicle Dynamics Module (VDM). The VDM responds to signals from various sensors in thevehicle to maintain the programmed ride height while the vehicle is either moving or stopped. This isaccomplished by opening and closing the solenoid valves to control the amount of air in the air spring(s). TheVDM controls the air compressor by applying voltage through the compressor relay to inflate the air spring(s) andraise the vehicle. The VDM opens the vent solenoid to lower the vehicle by releasing air from the air spring(s) inresponse to signal inputs from the air suspension height sensor. The VDM has a preprogramming trim height.

The load leveling feature automatically makes adjustments in vehicle height so that the vehicle is always attarget height and constant front-to-rear vehicle attitudes are maintained over the load range of the vehicle.

The system will remain active for 40 minutes after the ignition is turned off to make limited height adjustments asnecessary.

Air Suspension Disable Feature

The air suspension system can be disabled through the message center. Refer to Air Suspension SystemDisable/Enable in this section. When the driver elects to disable the air suspension system, the message centersends a message over the High Speed Controller Area Network (HS-CAN) bus to the VDM. Once the messageis received, the VDM will take no further action to inflate or deflate the air springs, below 15 mph. The system willremain ON or OFF when the ignition key is cycled.

When the air suspension system has been disabled, the message center will display SUSPENSION SWITCHEDOFF.

Air Compressor

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The air compressor:

consists of the compressor and vent solenoid; neither are serviced as individual items.is a single cylinder electric motor driven unit that provides pressurized air as required.is powered by an electromechanical relay, which is controlled by the VDM.passes pressurized air through the compressor air drier that contains silica gel (a drying agent).Moisture is then removed from the compressor air drier when vented air passes out of the systemduring vent operation.has a single port drier that can be serviced separately.

The vent solenoid:

allows air to escape from the system during venting actions.is part of the air compressor cylinder head.shares a common electrical connector with the air compressor motor.is enclosed in the cylinder head casting and forms an integral valve housing.has an O-ring seal that prevents air leakage past the dryer tip.opens when the VDM determines that lowering is required.provides an escape route for pressurized air when system pressures exceed safe operating levels.has a 1,034 kPa (150 psi) internal relief valve.is installed with the air compressor as a unit.

Air Spring

The air suspension system has 2 rear air springs. The air springs provide a varying spring rate proportional to thesystem air pressure and volume. The air suspension system regulates the air pressure in each air spring bycompressing and venting the air. Increasing air pressure (compressing) raises the vehicle; decreasing airpressure (venting) lowers the vehicle. Vehicle height is maintained by the addition and removal of air in each airspring through an air spring solenoid installed in the upper spring cap and energized through the VDM.

Air Tubes and Fittings

NOTE: Apply a soapy water solution to the air tubes to verify the location of air leaks. If the air tubes are cut,ruptured or leaking, a service repair kit is available.

Nylon air tubes with quick connect fittings connect to the air compressor and air spring solenoids. A Y-fitting isalso used to divide the air supply to the RH and LH air spring solenoids.

Air Suspension Height Sensors

There are 2 suspension height sensors used for the rear suspension. The sensors send a voltage signal to theVDM. The output ranges from approximately 4.5 volts at minimum height (when the vehicle is low or in full



jounce) to 0.5 volt at maximum height (when the vehicle is high or in full rebound).

The sensors have a usable range of Â±45 degrees. The sensors are mounted to the suspension at a point wherefull suspension travel at the wheel is relative to the travel at the height sensor. The sensors are mounted to theframe and the link is attached to a ball stud on the lower suspension arm. The left and right sensors haveopposite polarity and are not interchangeable.

When the height sensor indicates that the vehicle is lower than trim under normal driving conditions, the aircompressor will turn on and pump compressed air to the system. When the sensor indicates that the vehicle israised above trim under normal driving conditions, this will cause the air to be vented from the system to lowerthe vehicle to the trim height level.

Compressor Relay

An electromechanical relay is used in the air suspension system for compressor control. The relay switches highcurrent loads in response to low power signals and is controlled by the VDM.

The compressor relay is energized by the VDM to have high current flow from the battery to the compressormotor.

Vehicle Dynamics Module (VDM)

NOTICE: The Vehicle Dynamics Module (VDM) must receive a ride height adjustment calibration andpass a pneumatic test when it is installed new or swapped. Failure to follow these instructions will resultin the air suspension system operating incorrectly.

The VDM controls the air compressor motor (through an electromechanical relay), all air spring solenoids andprovides power to the rear height sensors. The VDM also controls vehicle height adjustments by monitoring the 2height sensors and other HS-CAN messages. The VDM conducts all fail-safe and diagnostic strategies andcontains self-test and communication software for testing the vehicle and related components.

The VDM monitors and controls the air suspension system through an 8-pin connector and a 16-pin connector.The connectors and the VDM are keyed so that the connectors cannot be plugged in incorrectly. The VDM usesthe HS-CAN communications network for sending and receiving various information.

Air Spring Solenoid

WARNING: Vent all air pressure from the air suspension system prior to disconnecting or removing anyair suspension components. It is dangerous to remove air suspension components while underpressure. Failure to follow this instruction may result in serious personal injury.

The air spring solenoid:

allows air to enter and exit the air spring during leveling operations.



is electrically operated and controlled by the VDM.is serviced separately from the air spring.

Inspection and Verification

1. Verify the customer concern.

2. NOTE: If the door ajar indicator is illuminated when all the doors, the liftgate and the liftgate glass areclosed, the air suspension will not work correctly. Repair the door ajar indicator. Refer to Section 413-01.

Visually inspect for obvious signs of mechanical and electrical damage.

Visual Inspection Chart

Mechanical Electrical

Restricted suspension movementExcessive vehicle loadDamaged or disconnected air tube(s) and/orfitting(s)Unmounted or damaged height sensor(s)Damaged rear air spring(s)Damaged solenoid valve(s)

Battery Junction Box (BJB) fuses:39 (60A)47 (30A)65 (10A)

Wiring, terminals or connectorsDamaged Vehicle Dynamics Module(VDM)

3. If an obvious cause for an observed or reported concern is found, correct the cause (if possible) beforeproceeding to the next step.

4. NOTE: Make sure to use the latest scan tool software release.

If the cause is not visually evident, connect the scan tool to the Data Link Connector (DLC).

5. NOTE: The Vehicle Communication Module (VCM) LED prove out confirms power and ground fromthe DLC are provided to the VCM.

If the scan tool does not communicate with the VCM:check the VDM connection to the vehicle.

check the scan tool connection to the VDM.

refer to Section 418-00, No Power To The Scan Tool, to diagnose no power to the scan tool.

6. If the scan tool does not communicate with the vehicle:

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verify the ignition key is in the ON position.

verify the scan tool operation with a known good vehicle.

refer to Section 418-00 to diagnose no response from the PCM.

7. Carry out the network test.If the scan tool responds with no communication for one or more modules, refer to Section418-00.

If the network test passes, retrieve and record continuous memory DTCs.

8. Clear the continuous DTCs and carry out the self-test diagnostics for the VDM. Refer to Self-Test inthis section.

9. If the DTCs retrieved are related to the concern, go to Vehicle Dynamics Module (VDM) DTC Chart.For all other DTCs, refer to the Master DTC Chart in Section 419-10.

10. If no DTCs related to the concern are retrieved, GO to Symptom Chart.

Pneumatic Test

This test verifies that the air tubes are connected and that they are not restricted. It also verifies that the aircompressor, air compressor vent solenoid and air spring solenoid valves are functioning correctly. This test isused to clear DTCs C1990 and C1991. Verify that the following conditions are met before running the PneumaticTest.

All the doors, the liftgate and the liftgate glass must be closed.The transmission is in PARK.The vehicle speed is less the 10 km/h (6 mph).The ignition switch is in the ON position.The air suspension system is enabled.Battery voltage is greater than 11 volts for the duration of the test.

1. Fulfill the pre-conditions.

2. Install a battery charger for the Pneumatic Test to prevent battery drain.

3. Using the scan tool, carry out the Pneumatic Test.

Trim Height Test (or Accurate Trim Test)

NOTE: The Trim Height Test is used to verify trim height only. If trim height needs to be adjusted, refer to RideHeight Adjustments in this section.



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The trim height test is used to make the vehicle level to within 2 mm (0.08 in) of the calibrated trim height. Anaccurate trim test should be run before setting vehicle alignment.

The following conditions must be met for the trim height test to run:

All the doors, the liftgate and the liftgate glass must be closed.The transmission is in PARK.The vehicle speed is less than 10 km/h (6 mph).The ignition switch is in the ON position.The air suspension system is enabled.Battery voltage is greater than 11 volts for the duration of the test.


2. Install a battery charger for the Trim Height Test to prevent battery drain.

3. Using the scan tool, carry out the Trim Height Test.

Self-Test

Verify that the following conditions are met before running the On-Demand Self Test.

All doors, the liftgate and the liftgate glass must be closed.The transmission is in PARK.The vehicle speed is less than 10 km/h (6 mph).The ignition switch is in the ON position.


2. Install a battery charger for the On-Demand Self Test to prevent battery drain.

3. Carry out the Vehicle Dynamics Module (VDM) On-Demand Self Test.

4. Record all listed DTCs.

5. Retrieve stored DTCs.

6. Troubleshoot any On-Demand Self Test DTCs first.

7. Repeat the On-Demand Self Test and clear DTCs after repairs are completed.

Vehicle Dynamics Module (VDM) DTC Chart

NOTE: Repair all other DTCs before repairing C1726. Repair DTCs C1990 and C1991 last.



DTCs Description Source Action

B1317 Battery Voltage High VehicleDynamicsModule(VDM)

GO to Pinpoint Test A.

B1318 Battery Voltage Low VDM GO to Pinpoint Test A.

B1342 ECU is Faulted VDM INSTALL a new VDM. REFER to Vehicle Dynamics Module (VDM)in this section. SET the ride height. REFER to Ride HeightAdjustments in this section. CARRY OUT the Pneumatic Test. TESTthe system for normal operation.

B1566 Door Ajar CircuitShort to Ground

VDM Doors/running boards open during self-test. VERIFY doors/runningboards signals are working. REFER to Section 417-02 for door ajarswitch diagnosis and Section 501-08 for retractable running boarddiagnosis.

B2477 Module ConfigurationFailure

VDM INSTALL a new VDM. REFER to Vehicle Dynamics Module (VDM)in this section. SET the ride height. REFER to Ride HeightAdjustments in this section. CARRY OUT the Pneumatic Test. TESTthe system for normal operation.

C1724 Air SuspensionHeight Sensor PowerCircuit Failure

VDM GO to Pinpoint Test B.

C1726 Air Suspension RearPneumatic Failure

VDM GO to Pinpoint Test C.

C1770 Air Suspension VentSolenoid OutputCircuit Failure

VDM GO to Pinpoint Test D.

C1790 Air Suspension LRAir Spring SolenoidOutput Circuit Failure

VDM GO to Pinpoint Test E.

C1795 Air Suspension RRAir Spring SolenoidOutput Circuit Failure

VDM GO to Pinpoint Test E.

C1810 Air SuspensionHeight Sensor DeltaOut of Range

VDM GO to Pinpoint Test K.

C1830 Air SuspensionCompressor RelayCircuit Failure

VDM GO to Pinpoint Test J.

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C1885 Air Suspension RRHeight Sensor CircuitFailure

VDM GO to Pinpoint Test F.

C1893 Air Suspension LRHeight Sensor CircuitFailure

VDM GO to Pinpoint Test F.

C1990 New Control ModuleInitialization (requiresride height calibrationand pneumatic testpass)

VDM REFER to Clearing DTC C1990 or C1991.

C1991 Plant Ride HeightSetting and/or TestsIncomplete

VDM REFER to Clearing DTC C1990 or C1991.

C1964 Compressor RunTime Exceeded

VDM GO to Pinpoint Test J.

C2001 Ride HeightCalibration Error

VDM ADJUST the ride height, REFER to Ride Height Adjustments in thissection. CLEAR the DTCs. REPEAT the self-test.

C2002 Pneumatic TestFailure

VDM VERIFY that all Pneumatic Test pre-conditions are met, REFER toPneumatic Test in this section. REPEAT the Pneumatic Test. If allconditions are met, the scan tool can communication with the VDMand the module is still unable to complete the Pneumatic Test, GOto Pinpoint Test C.

U0073 Control ModuleCommunication BusA Off

VDM REFER to Section 418-00 to diagnose the High Speed ControllerArea Network (HS-CAN) bus.

U0100 Lost Communicationwith PowertrainControl Module(PCM)

VDM REFER to Section 418-00 to diagnose the HS-CAN bus.

U0140 Lost Communicationwith Body ControlModule


U0155 Lost Communicationwith InstrumentCluster


U2011 Module TransmittedInvalid Data

VDM CLEAR the DTC. REPEAT the self-test.

If DTC U2011 returns, INSTALL a new VDM. REFER to Vehicle








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Dynamics Module (VDM) in this section. CLEAR the DTC. REPEATthe self-test.

U2050 Application NotPresent

VDM INSTALL a new VDM. REFER to Vehicle Dynamics Module (VDM)in this section. CLEAR the DTC. REPEAT the self-test.

Clearing DTCs C1990, C1991, C2001 and C2002

NOTE: Before proceeding with the following steps, make sure that the air suspension system is fully functional.The vehicle must pass the Pneumatic Test and have both ride height sensors calibrated for these codes to clear.

1. Connect the scan tool to the vehicle.

2. If C1990 or C1991 and C2002 are present, carry out the Pneumatic Test. The tester will indicate if thevehicle has passed the test.

3. NOTE: The vehicle must be on a level surface before calibrating the ride height sensors. Failure tofollow this instruction will result in system malfunction.

If C1990 or C1991 and C2001 are present, use the scan tool to manually raise and lower the vehicle tothe correct ride height on an alignment machine and calibrate the ride heights. Refer to Ride HeightAdjustments in this section.

4. Using the scan tool, retrieve the DTCs. Verify that all DTCs have been cleared.

5. Drive the vehicle and verify the repair. Verify that the message center does not display "CheckSuspension".

Symptom Chart

Symptom Chart

Condition Possible Sources Action

No communicationwith the VehicleDynamics Module(VDM)

Fuse(s)Wiring,terminals orconnectorsVDM

REFER to Section 418-00 to diagnosethe no communication problem.

NOTE: Make surethat the ignitionswitch is in the ON

Air suspensionsystemdisabled

VERIFY that the air suspension system isenabled. REFER to Air Suspension








position and the airsuspension isenabled beforedetermining that theVDM will not enterthe self-test.

Unable to enter self-test

System Disable/Enable in this section.REPEAT the self-test.

One or moreself-testpreconditionsnot fulfilled

VERIFY that all self-test preconditions arefulfilled, REFER to Self-Test in thissection. REPEAT the self-test. If allconditions are met and the scan toolcannot communicate with the VDM,REFER to Section 418-00 to diagnosethe no communication problem.

VDM VERIFY that all self-test preconditions aremet, REFER to Self-Test in this section.REPEAT the self-test. If all conditions aremet, the scan tool can communicate withthe VDM and the module is still unable toenter self-test, INSTALL a new VDM.REFER to Vehicle Dynamics Module(VDM) in this section.

Vehicle raises and/orlowers too slowly

DryerrestrictedCompressorvent solenoidAir tube(s)blocked orpinchedAir leaksAir springsolenoid(s)Air compressorassemblyVDM

GO to Pinpoint Test C.






Uneven vehicleheight

Air leaksWiring,terminals orconnectorsHeightsensor(s)Air springsolenoid(s)Air compressorassemblyAir tube(s)blocked orpinchedVDM

GO to Pinpoint Test C.

Air suspensionsystem leaks downat temperatures-30Â° C (-22Â° F) orbelow

Air suspensionsolenoid

CONFIRM that the condition occurs onlyat temperatures -30Â° C (-22Â° F) orbelow. INSTALL new air suspensionsolenoid(s) as necessary.

The air compressorruns continuouslywith the ignitionswitch in the OFFposition and no DTCis set

Wiring,terminals orconnectorsAir suspensionrelayVDM

GO to Pinpoint Test G.

The air suspensionsystem is inoperativewithout DTCs andwith the vehicle atrest

Fuse(s)Wiring,terminals orconnectorsHigh SpeedController AreaNetwork (HS-CAN) busnetworkcommunicationfaultDoor ajarswitch

GO to Pinpoint Test H.



Vehicle speedsignalVDM

Excessive aircompressor noise

Bracketisolator(s)MountingbracketAir compressorassemblyAir compressorassembly incontact withothercomponents

GO to Pinpoint Test I.

The air compressoris inoperative

Fuse(s)Air compressorassemblyWiring,terminals orconnectorsAir suspensionrelayVDM

GO to Pinpoint Test J.

Compressorrun timeexceeded

ALLOW the air compressor to cool for atleast 10 minutes. TEST the system fornormal operation.

Pinpoint Tests

NOTICE: Electronic modules are sensitive to electrostatic discharge. If exposed to these charges,damage to the module may result.

Refer to Inspection and Verification, the Vehicle Dynamics Module (VDM) DTC Chart and the Symptom Chart inthis section for direction to the appropriate pinpoint test.

Pinpoint Test A: DTC B1317 or B1318



Refer to Wiring Diagrams Cell 41, Vehicle Dynamic Suspension for schematic and connector information.

Normal Operation

The Vehicle Dynamics Module (VDM)) is supplied fused battery voltage through Battery Junction Box (BJB) fuse47 (30A) along circuit SBB47 (WH/RD), and fused ignition voltage through BJB fuse 65 (10A) along circuitCBB65 (WH/OG). A ground path is provided along circuits GD133 (BK) and GD120 (BK/GN).

DTC B1317 Battery Voltage High — With the ignition key in the RUN position, if battery voltageexceeds 18 volts for more than 500 ms, DTC B1317 will be set.DTC B1318 Battery Voltage Low — With the ignition key in the RUN position, if battery voltage fallsbelow 8.5 volts for more than 500 ms, DTC B1318 will be set.

This pinpoint test is intended to diagnose the following:Fuse(s)Wiring, terminals or connectorsVDM

PINPOINT TEST A: DTC B1317 OR B1318

NOTICE: Use the Flex Probe Kit for all test connections to prevent damage to the wiring terminals. Donot use standard multi-meter probes.

Test Step Result / Action to Take

A1 CHECK FOR ACTIVE DTCs

Repeat the self-test.Are the DTCs active?

Yes GO to A2.

No The system is operating correctly at this time. Concernmay have been caused by low battery or chargingsystem voltage. VERIFY that the battery and chargingsystem are OK. REFER to Section 414-00.

A2 CHECK THE BATTERY VOLTAGE

Measure the battery voltage between thepositive and negative battery posts with theKey ON Engine OFF (KOEO) and with theengine running.Is the battery voltage between 10 and 13volts with KOEO and between 11 and 16

Yes GO to A3.

No REPAIR the battery or charging system. REFER toSection 414-00. TEST the system for normaloperation.

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volts with the engine running?

A3 CHECK FOR VOLTAGE TO THE VDM

Disable the air suspension system. Refer toAir Suspension System Disable/Enable inthis section.Ignition OFF.Disconnect: VDM C2131a .Ignition ON.Both with the KOEO and with the enginerunning, measure the voltage betweenground and:

VDM C2131a-3, circuit CBB65(WH/OG), harness side.

VDM C2131a-11, circuit SBB47(WH/RD), harness side.

VDM C2131a-12, circuit SBB47(WH/RD), harness side.

Is the voltage between 10 and 13 voltswith KOEO, and between 11 and 16 voltswith the engine running?

Yes GO to A4.

No VERIFY BJB fuse 65 (10A) and fuse 47 (30A) are OK.If OK, REPAIR the affected circuit(s). If not OK,REFER to the Wiring Diagrams Manual to identify thepossible causes of the circuit short. CLEAR the DTCs.REPEAT the self-test.

A4 CHECK CIRCUITS GD133 (BK) AND GD120(BK/GN) FOR AN OPEN

Ignition OFF.Measure the resistance between ground and:

VDM C2131a-5, circuit GD133(BK), harness side.

Yes GO to A5.

No REPAIR the affected circuit(s). CLEAR the DTCs.REPEAT the self-test.




VDM C2131a-14, circuit GD120(BK/GN), harness side.

Is the resistance less than 5 ohms?

A5 CHECK THE VDM CONNECTOR

Check VDM C2131a for:corrosion.pushed-out pins.spread terminals.

Connect: VDM C2131a .Make sure the connector is seated correctlythen operate the system and verify theconcern is still present.Is the concern still present?

Yes INSTALL a new VDM. REFER to Vehicle DynamicsModule (VDM) in this section. CLEAR the DTCs.REPEAT the self-test.

No The system is operating correctly at this time. Concernmay have been caused by a loose or corrodedconnector.

Pinpoint Test B: DTC C1724


Normal Operation

The 2 rear height sensors receive a 5-volt reference voltage from the Vehicle Dynamics Module (VDM) alongcircuit LCL12 (VT/OG), both sensors share a common return path along circuit RCL12 (GN/WH). The RR sensorsends the suspension height voltage back to the VDM along circuit VCL12 (WH/VT) and the LR sensor sendsthe suspension height voltage back to the module along circuit VCL13 (BN/BU). The VDM monitors the 2 heightsensors and makes adjustments to the rear suspension based on sensor input.

DTC C1724 Air Suspension Height Sensor Power Circuit Failure — This DTC can be set during normaloperation and during the VDM on-demand self test. DTC C1724 will set during normal operation if the





ignition key is in the RUN position and the height sensor supply voltage is not at the expected level formore than 2 minutes. DTC C1724 will set during the on-demand self test if the height sensor voltage isnot detected after being enabled during the test.

This pinpoint test is intended to diagnose the following:Wiring, terminals or connectorsHeight sensor(s)VDM

PINPOINT TEST B: DTC C1724



B1 CHECK THE AIR SUSPENSION HEIGHT SENSORVOLTAGE PIDs

Disable the air suspension system. Refer to AirSuspension System Disable/Enable in this section.Connect the scan tool.Ignition ON.Enter the following diagnostic mode on the scan tool:DataLogger VDM .Disconnect the sensor arm linkage from both rear airsuspension height sensors.NOTE: The voltage will increase as the suspension iscompressed.Slowly move the height sensors through their fullrange of travel up and down while monitoring thefollowing PIDs:

Left Rear Height Sensor Voltage(LR_HEIGHT)

Right Rear Height Sensor Voltage(RR_HEIGHT)

Do the voltages vary from approximately 0.50 voltand 4.50 volts?

Yes INSPECT the height sensor electricalconnectors for corrosion and damage,REPAIR as necessary. CLEAR the DTCs.REPEAT the self-test.

No CONNECT the sensor arm linkages to theheight sensors.

For the LR height sensor, GO to B2.

For the RR height sensor, GO to B3.

B2 CHECK FOR VDM OUTPUT (LR HEIGHT SENSORVOLTAGE)

Ignition OFF.Yes




Disconnect: LR Height Sensor C4092 .Ignition ON.Measure the voltage between LR height sensorC4092-3, circuit LCL12 (VT/OG), harness side andground.

Are 5 volts present?

GO to B3.

No If less than 5 volts are present, GO to B4. Ifmore than 5 volts are present, GO to B6.

B3 CHECK FOR VDM OUTPUT (RR HEIGHT SENSORVOLTAGE)

Ignition OFF.Disconnect: RR Height Sensor C4093 .Ignition ON.Measure the voltage between RR height sensorC4093-3, circuit LCL12 (VT/OG), harness side andground.


Yes GO to B7.

No If less than 5 volts are present, GO to B4. Ifmore than 5 volts are present, GO to B6.

B4 CHECK CIRCUIT LCL12 (VT/OG) FOR AN OPEN

Ignition OFF.Disconnect: VDM C2131b .

Yes GO to B5.



For the RR height sensor, measure the resistancebetween VDM C2131b-4, circuit LCL12 (VT/OG),harness side and RR height sensor C4093-3, circuitLCL12 (VT/OG), harness side.For the LR height sensor, measure the resistancebetween VDM C2131b-4, circuit LCL12 (VT/OG),harness side and LR height sensor C4092-3, circuitLCL12 (VT/OG), harness side.


No REPAIR circuit LCL12 (VT/OG). CLEAR theDTCs. REPEAT the self-test.

B5 CHECK CIRCUIT LCL12 (VT/OG) FOR A SHORT TOGROUND

For the RR height sensor, measure the resistancebetween RR height sensor C4093-3, circuit LCL12(VT/OG), harness side and ground.For the LR height sensor, measure the resistancebetween LR height sensor C4092-3, circuit LCL12(VT/OG), harness side and ground.

Is the resistance greater than 10,000 ohms?

Yes GO to B7.

No REPAIR circuit LCL12 (VT/OG). CLEAR theDTCs. REPEAT the self-test.

B6 CHECK CIRCUIT LCL12 (VT/OG) FOR A SHORT TO



VOLTAGE

Ignition OFF.Disconnect: VDM C2131b .Ignition ON.For the LR height sensor, measure the voltagebetween LR height sensor C4092-3, circuit LCL12(VT/OG), harness side and ground.For the RR height sensor, measure the voltagebetween RR height sensor C4093-3, circuit LCL12(VT/OG), harness side and ground.Is any voltage present?

Yes REPAIR circuit LCL12 (VT/OG). CLEAR theDTCs. REPEAT the self-test.

No GO to B7.

B7 CHECK THE VDM CONNECTOR

Ignition OFF.Disconnect: VDM C2131b .Check the VDM connector for:

corrosion.pushed-out pins.spread terminals.

Connect: VDM C2131b .Make sure the connector is seated correctly, thenoperate the system and verify the concern is stillpresent.Is the concern still present?

Yes INSTALL a new VDM. REFER to VehicleDynamics Module (VDM) in this section.CLEAR the DTCs. REPEAT the self-test.

No The system is operating correctly at this time.Concern may have been caused by a looseor corroded connector.

Pinpoint Test C: Vehicle Raises and/or Lowers Too Slowly or Uneven Vehicle Height

Normal Operation

The air suspension height sensor sends a voltage signal to the Vehicle Dynamics Module (VDM). The outputranges from approximately 4.5 volts at minimum height (when the vehicle is low or in full jounce) to 0.5 volt atmaximum height (when the vehicle is high or in full rebound).

When the suspension height sensor indicates that the rear of the vehicle is lower or higher than trim height undernormal driving conditions, the VDM will command the air compressor and air solenoid valves to either fill or ventthe air springs depending on the input from the 2 height sensors. The air compressor sends the air to the airsprings first through the drier then along the air tubes, passing through a Y-fitting and connections, through theair solenoid valves and finally to the air springs.




DTC C1726 Air Suspension Rear Pneumatic Failure — With the ignition key in the RUN position, DTCC1726 will be set if the air suspension system attempts and fails to inflate (pump) or deflate (vent) aspecified number of times.DTC C2002 Pneumatic Test Failure — This DTC indicates that the Pneumatic Test has failed tocomplete, possibly due to mechanical or electrical failure of the air suspension system. DTCs C1990and/or C1991 will also set with this DTC.

This pinpoint test is intended to diagnose the following:Air leak(s)Air tube restricted or leak(s)Air tube(s)Mounting bracket(s)Air compressor drierAir spring solenoid valve(s)Height sensor(s)Air compressorAir spring(s)VDM

PINPOINT TEST C: VEHICLE RAISES AND/OR LOWERS TOO SLOWLY OR UNEVEN VEHICLE HEIGHT

NOTE: It may be necessary to vent air from the front air suspension air springs during this pinpoint test.


C1 CHECK THE AIR SUSPENSION HEIGHTSENSORS

Inspect the air suspension height sensors forcorrect installation.Inspect the air suspension height sensormounting brackets for damage.While listening for air leaks, verify that all airtubes are fully seated.Are the air suspension height sensors,mounting brackets and air tubes OK?

Yes GO to C2.

No REPAIR as necessary. If one or both height sensorassemblies are installed or repaired, both heightsensors must be calibrated. RESET the vehicle rideheight. REFER to Ride Height Adjustments in thissection. CLEAR the DTCs. REPEAT the self-test.

C2 CHECK THE AIR SUSPENSION HEIGHT SENSORVOLTAGE PIDs

Disable the air suspension system. Refer to AirSuspension System Disable/Enable in thissection.

Yes CONNECT the sensor arm linkages to the heightsensors. GO to C3.





Disconnect the sensor arm linkage from bothrear air suspension height sensors.Connect the scan tool.Ignition ON.Enter the following diagnostic mode on thescan tool: DataLogger VDM .NOTE: The voltage will increase as thesuspension is compressed.Slowly move the height sensors through theirfull range of travel up and down whilemonitoring the following PIDs:



Do the voltages vary from approximately0.50 volt and 4.50 volts?

No INSTALL a new height sensor(s) and CALIBRATEboth height sensors. REFER to Suspension HeightSensor in this section. CLEAR the DTCs. RESETthe vehicle ride height. REFER to Ride HeightAdjustments in this section. REPEAT the self-test.

C3 VERIFY THAT THE REAR OF THE VEHICLE CANBE RAISED

Toggle the LR and RR air spring solenoid(LR_SOL and RR_SOL) active commands ON.Toggle the air compressor (COMPRESSR)active command ON.While monitoring both height sensor voltagePIDs, allow the vehicle to raise for 30 to 45seconds.Toggle the VDM active commands OFF.Does the rear of the vehicle raise normallyand hold the new height?

Yes GO to C4.

No GO to C5.

C4 VERIFY THAT THE REAR OF THE VEHICLE CANBE LOWERED

Toggle the LR and RR air spring solenoid(LR_SOL and RR_SOL) active commands ON.Toggle the vent solenoid (As_Vent) activecommand ON.NOTE: Allow the rear to lower for 30 seconds.Toggle all active commands OFF.Does the rear lower normally?

Yes CARRY OUT the Pneumatic Test and VERIFYsystem operation.

No GO to C7.

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C5 CHECK OPERATION OF THE AIR COMPRESSOR

NOTICE: The Vehicle Dynamics Module(VDM) limits the air compressor run time. Ifthe air compressor overheats, it will notrestart until it cools down. The ignitionswitch must be in the OFF position to allowthe compressor thermal switch to cool.

Toggle the air compressor (COMPRESSR)active command ON.Does the air compressor run (slight buzzingnoise from RF corner of vehicle)?

Yes TOGGLE the COMPRESSR active command OFF.GO to C6.

No TOGGLE the COMPRESSR active command OFF.GO to Pinpoint Test J.

C6 CHECK THE AIR COMPRESSOR PRESSUREOUTPUT

NOTICE: The Vehicle Dynamics Module(VDM) limits the air compressor run time. Ifthe air compressor overheats, it will notrestart until it cools down. The ignitionswitch must be in the OFF position to allowthe compressor thermal switch to cool.

NOTE: If fluid is present when disconnecting anair tube, clear the air tubes. Refer to Air LineFluid Purge procedure in this section. Checkthe compressor air drier for water or the frontair spring for oil.

Disconnect the air tube at the air compressordrier.Connect an air pressure gauge (1,723 kPa[250 psi] maximum reading) with commonfittings to the air drier.NOTE: The vehicle will lower quickly.NOTE: When toggling the compressor ON, thevent solenoid will open as well. To prevent thevent solenoid from opening during this test,first toggle a single spring solenoid ON, thentoggle the compressor ON.Toggle the LR spring solenoid (LR_SOL) activecommand ON.

Yes GO to C8.

No INSTALL a new air suspension compressor. REFERto Air Suspension Compressor in this section.CARRY OUT the Pneumatic Test. VERIFY systemoperation.

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Toggle the air compressor (COMPRESSR)active command ON.Operate the air compressor for 30 secondsthen toggle the COMPRESSR active commandOFF.Did the compressor produce 1,034 kPa (150psi) within 30 seconds?

C7 CHECK THE PNEUMATIC SYSTEM — VENT THEAIR SPRINGS

NOTE: If fluid is present when disconnectingthe air tube, clear the air tubes. Refer to AirLine Fluid Purge in this section. Check the aircompressor drier for water or the aircompressor for oil contamination.

NOTE: The rear springs must be partiallyinflated in order to carry out this test. Add air asnecessary.

Disconnect the air tube at the air compressordrier.Toggle the LR air spring solenoid (LR_SOL)active command ON. This will activate both theLR and RR air spring solenoids.Does the air vent from the air compressordrier air tube?

Yes TOGGLE the LR_SOL active command OFF. GO toC9 .

No TOGGLE the LR_SOL active command OFF.

CONNECT the air tube to the air compressor drier.GO to C8.

C8 CHECK THE PNEUMATIC SYSTEM — AIR TUBE

NOTE: If fluid is present when disconnectingthe air tube, clear the air tubes. Refer to AirLine Fluid Purge in this section. Check the aircompressor drier for water or the aircompressor for oil contamination.

Disconnect the suspected rear air springsolenoid air tube.Connect the vacuum tester to the air tube andtry to pull a vacuum.Can a vacuum be developed?

Yes REPAIR or INSTALL a new air tube. CLEAR theDTC. REPEAT the self-test.

No GO to C11.

C9 CHECK THE VENT SOLENOID OPERATION





Disconnect the air tube at the drier.Connect the vacuum tester to the drier and tryto pull a vacuum.Toggle the vent solenoid (As Vent) activecommand ON.Try to pull a vacuum again.Can a vacuum be developed with the AsVent active command OFF and no vacuumdeveloped with the As Vent activecommand ON?


No If a vacuum can be developed with the ventsolenoid OFF, GO to C10 .

If a vacuum cannot be developed with the ventsolenoid OFF, INSTALL a new air compressor.REFER to Air Suspension Compressor in thissection.

C10 CHECK THE AIR TUBE AND CONNECTIONS

Check the air tube and connections betweenthe vacuum tester and the air compressor.Are the air tube and connections OK?

Yes INSTALL a new air compressor. REFER to AirSuspension Compressor in this section. CLEAR theDTC. REPEAT the self-test.

No REPAIR the air tube. GO to C9.

C11 CHECK THE SPRING SOLENOID VALVE

NOTE: The air springs must be inflated for thistest.

Disconnect the air tube at the air springsolenoids.Toggle the LR and RR air spring solenoid(LR_SOL and RR_SOL) active commands ON.Does air vent from the solenoids?

Yes TOGGLE the active commands OFF. INSTALL anew VDM. REFER to Vehicle Dynamics Module(VDM) in this section.

No TOGGLE the active commands OFF. INSTALL anew air spring solenoid. REFER to Air SpringSolenoid Valve in this section.

Pinpoint Test D: DTC C1770


Normal Operation

The Vehicle Dynamics Module (VDM) will command the air suspension system vent solenoid ON or OFF whencertain conditions are met. The VDM supplies voltage to the vent solenoid through circuit CCL14 (BN/VT), which





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activates the vent solenoid and vents the air suspension system. The vent solenoid is grounded through circuitGD123 (BK/GY).

The vent solenoid is part of the air suspension compressor, if a new vent solenoid is needed, an air suspensioncompressor must be installed.

DTC C1770 Air Suspension Vent Solenoid Output Circuit Failure — With the ignition in the RUNposition and during a deflate (vent) activity, if the VDM detects an open, a short to voltage or a short toground on the vent solenoid output circuit, DTC C1770 will be set.

This pinpoint test is intended to diagnose the following:Wiring, terminals or connectorsAir suspension compressorVDM

PINPOINT TEST D: DTC C1770



D1 CHECK THE VENT SOLENOID PIDs

Connect the scan tool.Ignition ON.Enter the following diagnostic mode on thescan tool: DataLogger VDM .Monitor the following VDM PIDs:

Vent solenoid output open circuit(VSOL_RLY_OC)

Vent solenoid output short tobattery (VSOL_RLY_STB)

Vent solenoid output short toground (VSOL_RLY_STG)

Do any of the PIDs display "Yes"?

Yes For a short to ground, GO to D3.

For a short to voltage, GO to D4.

For an open circuit, GO to D2.

No The condition is not present at this time. CLEAR theDTCs. REPEAT the self-test.

D2 CHECK CIRCUIT GD123 (BK/GY) FOR ANOPEN

Ignition OFF.Yes INSPECT the air suspension compressor C1179 forcorrosion and damage.



Disable the air suspension system. Refer toAir Suspension System Disable/Enable inthis section.Disconnect: Air Suspension CompressorC1179 .Measure the resistance between aircompressor assembly C1179-3, circuitGD123 (BK/GY), harness side and ground.


If the connector is corroded or damaged, REPAIR asnecessary.

If the connector is OK, GO to D5.

No REPAIR circuit GD123 (BK/GY). CLEAR the DTCs.REPEAT the self-test.

D3 CHECK THE VENT CONTROL CIRCUIT FOR ASHORT TO GROUND

Disable the air suspension system. Refer toAir Suspension System Disable/Enable inthis section.Ignition OFF.Disconnect: Air Suspension CompressorC1179 .Disconnect: VDM C2131a .Disable the air suspension system. Refer toAir Suspension System Disable/Enable inthis section.Measure the resistance between aircompressor C1179-4, circuit CCL14 (BN/VT),harness side and ground.

Yes GO to D5.

No REPAIR circuit CCL14 (BN/VT).

CLEAR the DTCs. REPEAT the self-test.






Is the resistance greater than 10,000ohms?

D4 CHECK THE VENT CONTROL CIRCUIT FOR ASHORT TO VOLTAGE

Disable the air suspension system. Refer toAir Suspension System Disable/Enable inthis section.Ignition OFF.Disconnect: Air Suspension CompressorC1179 .Disconnect: VDM C2131a .Ignition ON.Measure the voltage between air compressorC1179-4 circuit CCL14 (BN/VT) harness sideand ground.

Is any voltage present?

Yes REPAIR circuit CCL14 (BN/VT). CLEAR the DTCs.REPEAT the self-test.

No GO to D6.

D5 CHECK THE VENT SOLENOID FOR AN OPENOR A SHORT

Measure the resistance between aircompressor C1179 pin-4, component side

Yes GO to D6.




and C1179 pin-3, component side.Is the resistance between 17 and 22ohms?

No INSTALL a new air compressor. REFER to AirSuspension Compressor in this section. CLEAR theDTCs. REPEAT the self-test.

D6 CHECK THE VDM CONNECTOR

Ignition OFF.Check VDM C2131a for:


Connect: VDM C2131a .Make sure the connector is seated correctlythen operate the system and verify theconcern is still present.Is the concern still present?

Yes INSTALL a new VDM. REFER to Vehicle DynamicsModule (VDM) in this section. CLEAR the DTCs.REPEAT the self-test. Both height sensors must becalibrated. RESET the vehicle ride height. REFER toRide Height Adjustments in this section.


Pinpoint Test E: DTCs C1790 (LR) and C1795 (RR)


Normal Operation

The Vehicle Dynamics Module (VDM) will command the air spring solenoid(s) ON or OFF when certainconditions are met. The left solenoid receives voltage from the VDM along circuit CCL05 (WH/BN), the rightsolenoid receives voltage from the VDM along circuit CCL07 (YE/GY). The 2 solenoids share a common groundalong circuit GD120 (BK/GN).

C1790 LR Air Suspension Air Spring Solenoid Output Circuit Failure — With the ignition in the RUNposition and during a deflate (vent) or inflate (pump) activity, if the VDM detects an open, a short tovoltage or a short to ground on the LR air spring solenoid output circuit, DTC C1790 will be set.C1795 RR Air Suspension Air Spring Solenoid Output Circuit Failure — With the ignition in the RUNposition and during a deflate (vent) or inflate (pump) activity, if the VDM detects an open, a short tovoltage or a short to ground on the RR air spring solenoid output circuit, DTC C1795 will be set.

This pinpoint test is intended to diagnose the following:Wiring, terminals or connectorsAir spring solenoid(s)VDM







PINPOINT TEST E: DTCs C1790 (LR) AND C1795 (RR)



E1 CHECK THE AIR SPRING SOLENOID PID

Connect the scan tool.Ignition ON.Enter the following diagnostic mode on the scan tool:DataLogger VDM .Monitor the following VDM PIDs:

Left rear solenoid driver short to ground(LSOL_DR_STG)

Right rear solenoid driver short to ground(RSOL_DR_STG)

Do the PIDs indicate a short to ground?

Yes GO to E3.

No GO to E2.

E2 CHECK THE AIR SPRING SOLENOID CONNECTOR(S)

Disable the air suspension system. Refer to AirSuspension System Disable/Enable in this section.Using the DTCs obtained after running the VDM self-test, determine which air spring solenoid is causingthe concern.Ignition OFF.Disconnect: Suspect Air Spring Solenoid Connector .Inspect the pins and terminals of the air springsolenoid connector(s) for corrosion, damage,pushed-out pins, spread terminals, moisture or otherdamage.Is the air spring solenoid connector(s) OK?

Yes GO to E3.

No REPAIR the connector(s) as necessary.CLEAR the DTCs. REPEAT the self-test.

E3 CHECK THE AIR SPRING SOLENOID CONTROLCIRCUIT(S) FOR A SHORT TO GROUND

Disable the air suspension system. Refer to AirSuspension System Disable/Enable in this section.Ignition OFF.Disconnect: VDM C2131b .

Yes GO to E4.

No REPAIR the affected circuit(s).





Disconnect: Air Spring Solenoids C4044 LR andC4045 RR .Measure the resistance between C4044-1, circuitCCL05 (WH/BN), harness side and ground.

Measure the resistance between C4045-1, circuitCCL07 (YE/GY), harness side and ground.


CLEAR the DTCs. REPEAT the self-test.

E4 CHECK THE AIR SPRING SOLENOID CONTROLCIRCUIT FOR SHORT TO VOLTAGE

Disable the air suspension system. Refer to AirSuspension System Disable/Enable in this section.Ignition OFF.Disconnect: VDM C2131b .Disconnect: Air Spring Solenoids C4044 LR andC4045 RR .Ignition ON.For the LR air spring solenoid, measure thevoltage between C4044-1, circuit CCL05 (WH/BN),harness side and ground.

Yes REPAIR the affected circuit(s). CLEAR theDTCs. REPEAT the self-test.

No GO to E5.




For the RR air spring solenoid, measure thevoltage between C4045-1, circuit CCL07 (YE/GY),harness side and ground.


E5 CHECK CIRCUIT GD120 (BK/GN) FOR AN OPEN

Ignition OFF.For the RR air spring solenoid, measure theresistance between C4045-2, circuit GD120 (BK/GN),harness side and ground.

Yes GO to E6.

No REPAIR circuit GD120 (BK/GN). CLEAR theDTCs. REPEAT the self-test.



For the LR air spring solenoid, measure theresistance between C4044-2, circuit GD120 (BK/GN),harness side and ground.


E6 CHECK THE AIR SPRING SOLENOID COIL(S) FOR ANOPEN

For the RR air spring solenoid, measure theresistance between air spring solenoid C4045 pin-1,component side and air spring solenoid C4045 pin-2,component side.For the LR air spring solenoid, measure theresistance between air spring solenoid C4044 pin-1,component side and air spring solenoid C4044 pin-2,component side.Is the resistance between 15 and 19 ohms (if thesolenoid is very hot, the resistance may be ashigh as 22 ohms)?

Yes GO to E7.

No INSTALL a new air spring solenoid(s). REFERto Air Spring Solenoid Valve in this section.CLEAR the DTCs. REPEAT the self-test.

E7 CHECK THE VDM CONNECTOR

Check the VDM connector for:corrosion.pushed-out pins.spread terminals.

Connect: VDM C2131b .Make sure the connector is seated correctly thenenable the air suspension system, operate thesystem and verify the concern is still present.Is the concern still present?

Yes INSTALL a new VDM. REFER to VehicleDynamics Module (VDM) in this section.CLEAR the DTCs. REPEAT the self-test.

No The system is operating correctly at this time.Concern may have been caused by a loose orcorroded connector.

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Pinpoint Test F: DTCs C1893 (LR) and C1885 (RR)


Normal Operation

The 2 rear height sensors receive a 5-volt reference voltage from the Vehicle Dynamics Module (VDM) alongcircuit LCL12 (VT/OG), both sensors share a common return path along circuit RCL12 (GN/WH). The RR sensorsends the suspension height voltage back to the VDM along circuit VCL12 (WH/VT). The LR sensor sends thesuspension height voltage back to the module along circuit VCL13 (BN/BU). The VDM monitors the 2 heightsensors and makes adjustments to the rear suspension based on sensor input.

DTC C1883 Air Suspension LR Height Sensor Circuit Failure — With the ignition in the RUN position, ifthe height sensor is reading less than 0.5 volt or more than 4.5 volts, DTC C1883 will be set.DTC C1885 Air Suspension RR Height Sensor Circuit Failure — With the ignition in the RUN position,if the height sensor is reading less than 0.5 volt or more than 4.5 volts, DTC C1885 will be set.

This pinpoint test is intended to diagnose the following:Wiring, terminals or connectorsHeight sensor(s)VDM

PINPOINT TEST F: DTCs C1893 (LR) AND C1885 (RR)



F1 CHECK THE AIR SUSPENSION HEIGHT SENSORVOLTAGE PIDs

Disable the air suspension system. Refer to AirSuspension System Disable/Enable in thissection.Connect the scan tool.Ignition ON.Enter the following diagnostic mode on the scantool: DataLogger VDM .Disconnect the sensor arm linkage from both rearair suspension height sensors.

Yes INSPECT the height sensor electricalconnector(s) for corrosion and damage, REPAIRas necessary. CLEAR the DTCs. REPEAT theself-test.

No CONNECT the sensor arm linkages to the airsuspension height sensors. GO to F2.





NOTE: The voltage will increase as thesuspension is compressed.Slowly move the height sensors through their fullrange of travel up and down while monitoring thefollowing PIDs:



Do the voltages vary from approximately 0.50volt and 4.50 volts?

F2 CHECK CIRCUIT VCL12 (VT/OG) FOR VOLTAGE

Ignition OFF.Disconnect: Suspect Height Sensor .Ignition ON.For the LR height sensor, measure the voltagebetween LR height sensor C4092-3, circuitVCL12 (VT/OG), harness side and ground.

For the RR height sensor, measure the voltagebetween RR height sensor C4093-3, circuitVCL12 (VT/OG), harness side and ground.

Yes GO to F3.

No GO to Pinpoint Test B.




F3 CHECK CIRCUITS VCL13 (BN/BU) AND VCL12(WH/VT) FOR AN OPEN

Ignition OFF.Disconnect: VDM C2131b .For the LR height sensor, measure theresistance between VDM C2131b-6, circuitVCL13 (BN/BU), harness side and LR heightsensor C4092-2, circuit VCL13 (BN/BU), harnessside.

For the RR height sensor, measure theresistance between VDM C2131b-1, circuitVCL12 (WH/VT), harness side and RR heightsensor C4093-2, circuit VCL12 (WH/VT), harnessside.

Yes GO to F4.





F4 CHECK CIRCUITS VCL13 (BN/BU) AND VCL12(WH/VT) FOR A SHORT TO GROUND

For the LR height sensor, measure theresistance between LR height sensor C4092-2,circuit VCL13 (BN/BU), harness side and ground.

For the RR height sensor, measure theresistance between RR height sensor C4093-2,circuit VCL12 (WH/VT), harness side and ground.


Yes GO to F5.




F5 CHECK CIRCUITS VCL13 (BN/BU) AND VCL12(WH/VT) FOR A SHORT TO VOLTAGE

Ignition ON.For the LR height sensor, measure the voltagebetween LR height sensor C4092-2, circuitVCL13 (BN/BU), harness side and ground.For the RR height sensor, measure the voltagebetween RR height sensor C4093-2, circuitVCL12 (WH/VT), harness side and ground.


Yes REPAIR the affected circuit(s). CLEAR the DTCs.REPEAT the self-test.

No GO to F6.

F6 CHECK FOR SIGNAL RETURN SHORTED TOVOLTAGE

For the LR height sensor, measure the voltagebetween LR height sensor C4093-1, circuitRCL12 (GN/WH), harness side and ground.

For the RR height sensor, measure the voltagebetween RR height sensor C4092-1, circuitRCL12 (GN/WH), harness side and ground.

Yes GO to Pinpoint Test B.

No GO to F7.



Is 5 volts present?

F7 CHECK CIRCUIT RCL12 (GN/WH) FOR AN OPEN

Ignition OFF.For the LR height sensor, measure theresistance between VDM C2131b-5, circuitRCL12 (GN/WH), harness side and LR heightsensor C4092-1, circuit RCL12 (GN/WH),harness side.

For the RR height sensor, measure theresistance between VDM C2131b-5, circuitVCL12 (WH/VT), harness side and RR heightsensor C4093-2, circuit VCL12 (WH/VT), harnessside.

Yes GO to F8.

No REPAIR circuit VCL12 (WH/VT). CLEAR theDTCs. REPEAT the self-test.




F8 VERIFY HEIGHT SENSOR(S) OUTPUT VOLTAGE

Connect: VDM C2131b .Connect: RH Height Sensor C4093 and LHHeight Sensor C4092 .Disable the air suspension system. Refer to AirSuspension System Disable/Enable in thissection.Back probe RR height sensor C4093-2, circuitVCL12 (WH/VT) and LR height sensor C4092-2,circuit VCL12 (WH/VT).Is the voltage reading the same as the sensorPID reading?

Yes GO to F9.

No INSTALL a new height sensor(s) and CALIBRATEboth height sensors. REFER to SuspensionHeight Sensor in this section, CLEAR the DTCs.REPEAT the self-test.

F9 CHECK THE VDM CONNECTOR

Disconnect: VDM C2131b .Check VDM C2131b for:


Connect: VDM C2131b .Make sure the connector is seated correctly thenenable the air suspension system, operate thesystem and verify the concern is still present.Is the concern still present?

Yes INSTALL a new VDM. REFER to VehicleDynamics Module (VDM) in this section. CLEARthe DTCs. REPEAT the self-test.

No The system is operating correctly at this time.Concern may have been caused by a loose orcorroded connector.

Pinpoint Test G: The Air Compressor Runs Continuously With the Ignition Switch in the OFF Position

Normal Operation


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With the air suspension system activated and the ignition switch in the ON position, the Vehicle DynamicsModule (VDM) uses input from the 2 suspension height sensors to determine if vehicle payload has changedenough to warrant the adjustment of the rear suspension. If an adjustment is necessary, the VDM will open theair spring solenoids and activate the air compressor to inflate the air springs and raise the rear suspension. Todeflate the air springs and lower the rear suspension, the VDM will open the air spring solenoids and activate thevent solenoid.

With the air suspension system deactivated and the ignition switch in the OFF position, the VDM will ignoreheight sensor input and not adjust the rear suspension. When only the ignition switch is placed in the OFFposition, the VDM will remain powered for approximately 40 minutes to allow the system to adjust the rearsuspension due to changes in vehicle payload. Once the 40 minutes has elapsed, the VDM will depower andignore any height sensor input until the ignition switch is placed in the ON position.

To activate the air compressor, the VDM supplies voltage to the air compressor relay along circuit CCL01(WH/VT). This voltage passes through the coil side of the relay and to ground along circuit GD123 (BK/GY),which energizes the relay. The switch side of the relay receives fused battery voltage from Battery Junction Box(BJB) fuse 39 (60A) along circuit SBB39 (WH/RD). When the relay is energized, the switch side closes and thisfused battery voltage is sent to the air compressor along circuit CCL08 (BU/BN). The voltage passes through theair compressor and to ground along circuit GD123 (BK/GY), which activates the air compressor.

This pinpoint test is intended to diagnose the following:Wiring, terminals or connectorsAir compressor relayVDM

PINPOINT TEST G: THE AIR COMPRESSOR RUNS CONTINUOUSLY WITH THE IGNITION SWITCH IN THE OFF POSITION


G1 CHECK THE RELAY CONTROL CIRCUIT FOR A SHORTTO VOLTAGE

Disable the air suspension system. Refer to AirSuspension System Disable/Enable in this section.Ignition OFF.Disconnect: VDM C2131a .Remove the air compressor relay.Ignition ON.Measure the voltage between air compressor relay,circuit CCL01 (WH/VT), harness side and ground.

Yes REPAIR circuit CCL01 (WH/VT). CLEAR theDTCs. REPEAT the self-test.

No GO to G2.





G2 CHECK FOR MODULE ACTIVITY

NOTE: If the key has been off for 39 minutes and 30seconds, the compressor is permitted to run once fora maximum of 30 seconds.

Ignition OFF.Connect: VDM C2131a .Connect: Air Compressor Relay .Enable the air suspension. Refer to Air SuspensionSystem Disable/Enable in this section.Ignition ON.Ignition OFF.Verify the air compressor still cycles for a maximumof 30 seconds after the ignition is turned OFF.Does the air compressor still cycle for greaterthan 30 seconds after the ignition is turned OFF?

Yes GO to G3.

No The system is OK. INFORM the owner ofsystem operations.

G3 CHECK THE VDM

Disable the air suspension system. Refer to AirSuspension System Disable/Enable in this section.Disconnect: VDM C2131a .

Yes GO to G4.

No





Disconnect: VDM C2131b .Does the air compressor still cycle?

INSTALL a new VDM. REFER to VehicleDynamics Module (VDM) in this section.REPEAT the self-test.

G4 CHECK CIRCUIT CCL08 (BU/BN) FOR A SHORT TOVOLTAGE

Disconnect: Air Compressor Relay .Does the air compressor still cycle?

Yes REPAIR circuit CCL08 (BU/BN). TEST thesystem for normal operation.

No INSTALL a new air compressor relay. TESTthe system for normal operation.

Pinpoint Test H: The Air Suspension System is Inoperative Without DTCs and with the Vehicle at Rest

Normal Operation

The scan tool is used to communicate with the Vehicle Dynamics Module (VDM) and run the self-test. The VDMis supplied fused battery voltage through Battery Junction Box (BJB) fuse 47 (30A) along circuit SBB74(WH/RD), and fused ignition circuit through BJB fuse 65 (10A) along circuit CBB65 (WH/OG). A ground path isprovided for the module along circuits GD120 (BK/GN) and GD133 (BK). The VDM communicates with the othermodules along the High Speed Controller Area Network (HS-CAN). The VDM must receive inputs from severaldifferent components before it will allow the vehicle dynamic suspension system to operate.

This pinpoint test is intended to diagnose the following:Fuse(s)Wiring, terminals or connectorsDoor switch is indicating door ajar statusVehicle speed signalSystem is not enabledVDM

PINPOINT TEST H: THE AIR SUSPENSION SYSTEM IS INOPERATIVE WITHOUT DTCs AND WITH THE VEHICLE AT REST

NOTE: If the vehicle has been sitting with the key in the run position, it may be necessary to open and close thedriver side door. This will enable the system to carry out the pump or vent functions quicker.


H1 VERIFY THAT THE SYSTEM ISENABLED




Verify that the air suspensionsystem is enabled. Refer to AirSuspension SystemDisable/Enable in this section.Is the air suspension systemenabled?

Yes GO to H2.

No ENABLE the air suspension system. REFER to Air SuspensionSystem Disable/Enable in this section.

H2 CHECK THE VDM IGNITION SWITCH(IGN_RUN) PID

Connect the scan tool.Ignition ON.Enter the following diagnostic modeon the scan tool: DataLogger VDM.While cycling the ignition key fromON to OFF and then back to ON,monitor the IGN_RUN PID.Does the PID display NO with thekey in the OFF position and YESwith the key in the ON position?

Yes GO to H3.

No VERIFY BJB fuse 65 (10A) is OK. If OK, REPAIR circuit CBB65(WH/OG). If not OK, REFER to the Wiring Diagrams Manual toidentify the possible causes of the circuit short. TEST thesystem for normal operation.

H3 CHECK THE VDM DRIVER DOORAJAR SWITCH (D_DR_SW) PID

Ignition ON.Monitor VDM door ajar PID.Close all the doors, liftgate, liftgateglass and power running boards.While monitoring the D_DR_SWPID, open and close the driverdoor.Does the PID change fromCLOSED to OPEN?

Yes GO to H4.

No REFER to Section 418-01 to diagnose the High SpeedController Area Network (HS-CAN) concern.

H4 CHECK THE VDM VSS PID

Monitor the VSS PID.Test drive the vehicle at differentspeeds.Does the VSS PID match thespeedometer within 8 km/h (5mph)?

Yes GO to H5.

No REFER to Section 418-01 to diagnose the HS-CAN concern.



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H5 CHECK THE VDM CONNECTORS

Ignition OFF.Disconnect: VDM C2131a .Disconnect: VDM C2131b .Check the VDM connectors for:


Connect: VDM C2131a .Connect: VDM C2131b .Make sure the connectors areseated correctly then enable the airsuspension system, operate thesystem and verify the concern isstill present.Is the concern still present?

Yes GO to H6.

No The system is operating correctly at this time. Concern mayhave been caused by a loose or corroded connector.

H6 VERIFY THE SYSTEMS OPERATION

Using the scan tool, carry out thePneumatic Test.Does running the Pneumatic Testgenerate any DTCs?

Yes RECORD the DTCs and REFER to the Vehicle DynamicsModule (VDM) DTC Chart.

No The system is operating correctly at this time. Concern mayhave been caused by a loose or corroded connector.

Pinpoint Test I: Excessive Air Compressor Noise

Normal Operation

The air compressor is isolated from the rest of the vehicle and other components by 3 rubber isolators and abracket. The bracket is mounted to the vehicle using 3 rubber isolators with metal inserts. The air compressorshould not be in contact with the vehicle or other components.

This pinpoint test is intended to diagnose the following:Compressor bracketBracket isolatorsCompressor mountsComponent routingWire harness routing



PINPOINT TEST I: EXCESSIVE AIR COMPRESSOR NOISE


I1 CHECK FOR THE AIR COMPRESSOR AND/OR THE AIRCOMPRESSOR WIRING CONTACTING OTHERCOMPONENTS

Check the air compressor wiring to see if it iscontacting other components inside the enginecompartment at any place other than the mountingpoints.Check for anything contacting the air compressor(other wire harnesses, air tubes, hoses, loosefasteners, stones or other foreign material).Check for any contact between the wire harness andother compressor components.Is any portion of the wire harness contacting thecompressor motor components or is anythingcontacting the compressor assembly other thanthe mounts?

Yes REMOVE the air compressor assembly,REFER to Air Suspension Compressor inthis section. ADJUST the air compressorwiring harness so that it does not contact thecompressor motor or FASTEN/REMOVEobjects so they no longer contact the aircompressor assembly.

INSTALL the air compressor assembly,REFER to Air Suspension Compressor inthis section. TEST the system for normaloperation.

No GO to I2.

I2 CHECK FOR A BENT AIR COMPRESSOR BRACKET

Check the air compressor bracket for anydamage/bends that may contact other componentswithin the engine compartment.Check the bracket rubber isolators and inserts for anyexcessive wear or damage.Is the air compressor bracket making contact withother components or are the bracket isolatorsdamaged?

Yes INSTALL a new air compressor assembly orREPAIR other components as necessary.REFER to Air Suspension Compressor inthis section. TEST the system for normaloperation.

No GO to I3.

I3 CHECK THE AIR COMPRESSOR MOUNTS FOR DAMAGE

Check the air compressor mounts for signs of cracksor tearing away from the inner sleeve.Is damage present in the mounts?

Yes INSTALL a new air compressor assembly.REFER to Air Suspension Compressor inthis section. TEST the system for normaloperation.







No GO to I4.

I4 CHECK THE AIR COMPRESSOR FOR NOISE

NOTICE: Do not run the air compressor for morethan 3 minutes. The air compressor can overheatand stop operating due to an internal temperaturesensitive thermal breaker. The Vehicle DynamicsModule (VDM) will limit run time to protect the aircompressor. When DTC C1964 is present, thecompressor will not operate for approximately 10minutes.

Remove the air compressor assembly, but leave itconnected electrically. Refer to Air SuspensionCompressor in this section.Connect the scan tool.Ignition ON.Enter the following diagnostic mode on the scan tool:DataLogger VDM .Toggle the VDM air compressor (COMPRESSR)active command ON.Is the air compressor exhibiting any unusualnoise?

Yes TOGGLE the COMPRESSR activecommand OFF. INSTALL a new aircompressor. REFER to Air SuspensionCompressor in this section. TEST the systemfor normal operation.

No TOGGLE the COMPRESSR activecommand OFF. RECHECK the mountingsand bracket for damage. If damaged,INSTALL a new air compressor bracket.REFER to Air Suspension Compressor inthis section. TEST the system for normaloperation.

Pinpoint Test J: The Air Compressor is Inoperative


Normal Operation

The Vehicle Dynamics Module (VDM) will activate the air compressor once certain conditions are met. Toactivate the air compressor, the VDM supplies voltage to the air compressor relay along circuit CCL01 (WH/VT).This voltage passes through the coil side of the relay and to ground along GD123 (BK/GY), which energizes therelay. The switch side of the relay receives fused battery voltage from Battery Junction Box (BJB) fuse 39 (60A)along circuit SBB39 (WH/RD). When the relay is energized, the switch side closes and this fused battery voltageis sent to the air compressor along circuit CCL08 (BU/BN). The voltage passes through the air compressor andto ground along circuit GD123 (BK/GY), which activates the air compressor.

To protect the air compressor from damage due to excessive run time and heat build up, the air compressorassembly contains a temperature sensitive, thermal circuit breaker and the VDM contains software to monitor







how long the compressor has been running. The circuit breaker will protect the compressor from damage due tooverheating by disabling the compressor when the compressor reaches a pre-determined temperature threshold.Once the compressor has had sufficient time to cool, approximately 10 minutes, the circuit breaker will reset andallow the compressor to function. The VDM will also monitor the amount of time the air compressor runs. Oncethe run time has reached a pre-determined limit, the VDM will set DTC C1964 and disable the air compressoruntil it has had sufficient time to cool down.

DTC C1830 (Air Compressor Relay Circuit Failure) — With the ignition in the RUN position and duringa deflate (vent) or inflate (pump) event, if the VDM detects an open, a short to voltage or a short toground on circuit CCL01 (WH/VT), DTC C1830 will be set.DTC C1964 (Compressor Run Time Exceeded) — With the ignition in the RUN position and during aninflate (pump) event, if the air compressor exceeds a pre-determined run time limit, DTC C1964 will beset.

This pinpoint test is intended to diagnose the following:Fuse(s)Wiring, terminals or connectorsAir compressor relayAir compressorVDM

PINPOINT TEST J: THE AIR COMPRESSOR IS INOPERATIVE



J1 ISOLATE THE AIR COMPRESSOR RELAY

Carry out the mini-ISO relay component test.Refer to Wiring Diagrams Cell 149 forcomponent testing.

Inspect the relay and socket for corrosion,pushed-out pins and spread terminals.Does the air compressor relay pass thetest and are the relay and socket OK?

Yes GO to J2.

No REPAIR or INSTALL a new air compressor relay asnecessary. CLEAR the DTC. REPEAT the self-test.

J2 CHECK VDM DTCs

Review the VDM DTCs retrieved duringInspection and Verification.Are any VDM DTCs present?

Yes If only DTC C1964 is present, ALLOW the aircompressor a minimum of 10 minutes to cool. CLEARthe DTCs. REPEAT the self-test.

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If DTC C1830 is present, GO to J7.

If DTC C1726 is present, GO to J3.

For all other DTCs, GO to the Vehicle DynamicsModule (VDM) DTC Chart.

No GO to J3.

J3 CHECK THE VOLTAGE TO THE AIRCOMPRESSOR RELAY

NOTE: Make sure the battery voltage isgreater than 10 volts before testing thecompressor relay voltage.

Ignition OFF.Disconnect: Air Compressor Relay .Measure the voltage between air compressorrelay, circuit SBB39 (WH/RD), harness sideand ground.

Yes GO to J4.

No VERIFY BJB fuse 39 (60A) is OK. If OK, REPAIRcircuit SBB39 (WH/RD). If not OK, REFER to theWiring Diagrams manual to identify the possiblecauses of the circuit short. CLEAR the DTCs.REPEAT the self-test.



Is the voltage greater than 10 volts?

J4 CHECK CIRCUIT CCL08 (BU/BN) FOR AN OPEN

Disconnect: Air Compressor AssemblyC1179 .Measure the resistance between aircompressor relay, circuit CCL08 (BU/BN),harness side and air compressor assemblyC1179-2, circuit CCL08 (BU/BN), harnessside.


Yes GO to J5.

No REPAIR circuit CCL08 (BU/BN). CLEAR the DTCs.REPEAT the self-test.

J5 CHECK THE COMPRESSOR GROUND CIRCUITFOR AN OPEN

Measure the resistance between aircompressor assembly C1179-1, circuitGD123 (BK/GY), harness side and ground.

Yes GO to J6.

No REPAIR circuit GD123 (BK/GY). TEST the system fornormal operation.




J6 ISOLATE THE AIR COMPRESSOR

NOTICE: Do not run the air compressor formore than 3 minutes. The air compressorcan overheat and stop operating due to aninternal temperature sensitive thermalbreaker.

Connect: Air Compressor Assembly C1179 .Install a fused jumper wire between aircompressor relay, circuit SBB39 (WH/RD)and circuit CCL08 (BU/BN).Does the air compressor run?

Yes REMOVE the jumper wire. GO to J11.

No REMOVE the jumper wire. INSTALL a new aircompressor. REFER to Air Suspension Compressor inthis section. CLEAR the DTCs. REPEAT the self-test.

J7 CHECK THE RELAY CONTROL CIRCUIT FOR ASHORT TO VOLTAGE

Disable the air suspension system. Refer toAir Suspension System Disable/Enable inthis section.Ignition OFF.Disconnect: VDM C2131a .Disconnect: Air Compressor Relay .Ignition ON.Measure the voltage between air compressorrelay, circuit CCL01 (WH/VT), harness sideand ground.

Yes REPAIR circuit CCL01 (WH/VT). CLEAR the DTCs.REPEAT the self-test.

No GO to J8.






J8 CHECK THE RELAY CONTROL CIRCUIT FOR ASHORT TO GROUND

Ignition OFF.Measure the resistance between aircompressor relay, circuit CCL01 (WH/VT),harness side and ground.

Yes GO to J9.

No REPAIR circuit CCL01 (WH/VT). CLEAR the DTCs.REPEAT the self-test.



Is the resistance greater than 10,000ohms?

J9 CHECK THE RELAY CONTROL CIRCUIT FORAN OPEN

Measure the resistance between aircompressor relay, circuit CCL01 (WH/VT)and VDM C2131a-6, circuit CCL01 (WH/VT),harness side.

Yes GO to J10.

No REPAIR circuit CCL01 (WH/VT). CLEAR the DTCs.REPEAT the self-test.




J10 CHECK THE AIR COMPRESSOR RELAYGROUND FOR AN OPEN

Disconnect: Air Compressor Relay .Measure the resistance between aircompressor relay, circuit GD123 (BK/GY),harness side and ground.

Yes GO to J11.

No REPAIR circuit GD123 (BK/GY). CLEAR the DTCs.REPEAT the self-test.




J11 CHECK THE VDM OPERATION

Check the VDM connector for:corrosion.pushed-out pins.spread terminals.

Connect: VDM C2131a (if previouslydisconnected) .Connect: Air Compressor Relay (if previouslydisconnected) .Make sure the connectors are seatedcorrectly then enable the air suspensionsystem. Refer to Air Suspension SystemDisable/Enable in this section.Operate the system and verify the concern isstill present.Is the concern still present?



Pinpoint Test K: DTC C1810

Normal Operation





The 2 rear height sensors receive a 5-volt reference voltage from the Vehicle Dynamics Module (VDM) alongcircuit LCL12 (VT/OG), both sensors share a common return path along circuit RCL12 (GN/WH). The RR sensorsends the suspension height voltage back to the VDM along circuit VCL12 (WH/VT). The LR sensor sends thesuspension height voltage back to the module along circuit VCL13 (BN/BU). The VDM monitors the 2 heightsensors and makes adjustments to the rear suspension based on sensor input.

DTC C1810 Air Suspension Height Sensor Delta Out Of Range — When performing a self-test, a rideheight adjustment or when the VDM adjusts the ride height through normal operation, if the left andright calculated ride height value differs by 100 mm (3.93 in) or more, DTC C1810 will be set.

This pinpoint test is intended to diagnose the following:Vehicle lean (air spring leak, asymmetric loading)Height sensor bracket bent or looseHeight sensor link arm bent, loose or disconnectedHeight sensor(s) out of calibrationAir tube restriction

PINPOINT TEST K: DTC C1810


K1 VERIFY THAT DTC C1810 IS PRESENT ANDACTIVE

NOTE: The VDM will log DTC C1810 ifthe left and right calculated ride heightvalue differs by 100 mm (3.93 in) ormore.

Connect the scan tool.Ignition ON.Carry out the Pneumatic Test.Does DTC C1810 set after carryingout the Pneumatic Test?

Yes GO to K2.

No GO to K3.

K2 INSPECT THE RH AND LH HEIGHTSENSORS

Verify that both height sensor arms arefastened to the ball studs on the heightsensor(s) and lower control arm(s).Verify that the height sensor arms areinstalled correctly, and not positioned on

Yes INSTALL new component(s) as necessary, RESET thevehicle ride height. REFER to Ride Height Adjustments inthis section. REPEAT the self-test.




backwards.Inspect for loose or bent height sensor(s)and height sensor(s) arms.Are any of the height sensorcomponents damaged?

No GO to K3.

K3 CHECK THE VEHICLE FORASYMMETRICAL LOADING

Check for unbalanced or heavy load onone side of the vehicle.Is the vehicle heavily loaded on oneside causing the ride height to beincorrect?

Yes REPAIR the loading issue and REPEAT the self-test.

No GO to K4.

K4 CHECK FOR VEHICLE LEANING

Ignition OFF.Position the vehicle on a level surface.Using the scan tool, carry out theAccurate Trim Test.Are both the LR and RR ride heightswithin specification?

Yes GO to K7.

No GO to K5.

K5 CHECK THE HEIGHT SENSOR OPERATIONDURING PUMP

Using the scan tool, inflate the system tofor 30 seconds and monitor the followingPIDs:

Left Rear Height SensorVoltage (LR_HEIGHT)

Right Rear Height SensorVoltage (RR_HEIGHT)

Does the system inflate evenly?

Yes GO to K6.

No GO to Pinpoint Test C.

K6 CHECK HEIGHT SENSOR OPERATIONDURING VENT

Using the scan tool, command thesystem to vent for 20 seconds andmonitor the following PIDs:

Yes GO to K7.

No GO to Pinpoint Test C.



Left Rear Height SensorVoltage (LR_HEIGHT)

Right Rear Height SensorVoltage (RR_HEIGHT)

Does the system deflate evenly?

K7 CHECK THE AIR SPRING(S) FOR LEAKS.

Inspect both the LR and RR air spring forleaks.Are any leaks present?

Yes REPAIR the leaks, REPEAT the self-test.

No System operating correctly at this time.

Component Test

Relay

Refer to Wiring Diagrams Cell 149 for component testing.

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Documents

A i r S p r i n g A i r Tu b e s a n d F i t t i n g s N O ... · Trim Height Test (or Accurate Trim Test) Self-Test Vehicle Dynamics Module (VDM) DTC Chart Symptom Chart Pinpoint