Desired Speed Input (4 - 20 MA)

8/11/2019 Desired Speed Input (4 - 20 MA)

1/15

Shutdown SIS

Previous Screen

Product: GENERATOR SET

Model: G3520B GENERATOR SET GZP

Configuration: G3520B Generator Set GZP00001-UP

TroubleshootingG3520B Engines

Media Number -RENR5927-05 Publication Date -01/05/2006 Date Updated -25/05/2006

i01893588

Desired Speed Input (4 - 20 mA)

SMCS -1901-038

System Operation Description:

Note: For this troubleshooting procedure, the "Desired Speed Input" configuration parameter must be setto "4-20 mA Input" in the "Service/Configuration" screen of the Caterpillar Electronic Technician (ET).Do not select "PWM". The master Electronic Control Module (ECM) cannot be configured to accept aPWM input signal for control of the engine speed.

The selection of the "4-20 mA Input" setting requires a 4 to 20 mA signal for regulation of the desiredengine speed. If the "Desired Speed Input" is set to "0-5 VDC Input", do not use this procedure totroubleshoot the circuit.

When the desired speed input is correspondingly configured, the master ECM controls the engine speedaccording to the 4 to 20 mA current.

The value of the current corresponds to a range of desired engine speeds between minimum high idleand maximum high idle. The "Minimum Engine High Idle Speed" and the "Maximum Engine High IdleSpeed" are set with the "Service/Configuration" screen of ET. For more information, refer to SystemsOperation/Testing and Adjusting, "Electronic Control System Parameters".

When the "Idle/Rated" switch is in the Rated position, a current value of 4.0 mA corresponds to theprogrammed "Minimum Engine High Idle Speed". A current value of 20.0 mA corresponds to"Maximum Engine High Idle Speed". Current values within this range will vary the desired engine speed

in a linear fashion between "Minimum Engine High Idle Speed" and "Maximum Engine High IdleSpeed".

Current values that are greater than 22.0 mA will activate the "524-03 Desired Engine Speed Sensorshort to +batt" diagnostic code. Current values that are less than 2.0 mA will activate the "524-04Desired Engine Speed Sensor short to ground" diagnostic code.

The most likely causes of the diagnostic code are a poor connection or a problem in a wiring harness.The next likely cause is a problem with a component. The least likely cause is a problem with the masterECM.

Pgina 1 de 15G3520B Generator Set GZP00001-UP(SEBP3867 - 14) - Documentation

22/04/2014


2/15

Logged diagnostic codes provide a historical record. Before you begin this procedure, use ET to printthe logged codes to a file.

The troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correctingthe cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.

Illustration 1 g00993477

Schematic of the 4 to 20 mA desired speed input

Test Step 1. Inspect the Electrical Connectors and Wiring

A. Set the engine control to the OFF/RESET mode. Switch the 16 amp circuit breaker OFF.

Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".


22/04/2014


3/15


Terminal box for the master ECM

(1) 16 amp circuit breaker

(2) J1/P1 connectors for the master ECM

(3) J9/P9 connectors

B. Thoroughly inspect the following components:

ECM J1/P1 connectors

J9/P9 connectors on the terminal box

Wiring and the connections between the terminal box and the device that supplies the 4 to20 mA signal

a. Check the torque of the Allen head screw for the master ECM connectors. The propertorque is 6 1 Nm (55 9 lb in).


22/04/2014


4/15


Harness side of the master ECM P1 connector

(P1-36) + Signal

(P1-37) - Signal


Harness side of the P9 connector

(P9-K) + Signal

(P9-P) - Signal


22/04/2014


5/15

b. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the 4 to 20 mAcircuit.

c. Check the harness and wiring for abrasion and pinch points between the device that suppliesthe 4 to 20 mA signal and the master ECM.

Expected Result:

All connectors, pins, and sockets are connected properly. The connectors and the wiring do not havecorrosion, abrasion, or pinch points.

Results:

OK - The components are in good condition with proper connections. If you are troubleshooting a"524-03 Desired Engine Speed Sensor short to +batt" diagnostic code, proceed to Test Step 2. Ifyou are troubleshooting a "524-04 Desired Engine Speed Sensor short to ground" diagnostic code,proceed to Test Step 5.

Not OK - The components are not in good condition and/or at least one connection is improper.

Repair: Perform the necessary repairs and/or replace parts, if necessary.

STOP

Test Step 2. Check for an Open Circuit

A. Remove the two wires ("+" and "-") for the 4 to 20 mA signal from the device that supplies the 4to 20 mA signal.

B. Install a jumper wire between the two wires ("+" and "-") that were removed from the device thatsupplies the 4 to 20 mA signal.

C. Disconnect the P1 connector from the master ECM.


22/04/2014


6/15


ECM side of the P1 connector

(P1-36) + Signal

(P1-37) - Signal

D. Use an ohmmeter to measure the resistance between terminals P1-36 and P1-37 on the ECM sideof the P1 connector.

Expected Result:

The resistance is less than 5 ohms.

Results:

OK - The resistance is less than 5 ohms. The circuit is not open.


22/04/2014


7/15

Repair: Remove the jumper wire. Insulate the wire leads with electrical tape in order to ensurethat the leads do not create a short circuit.

Proceed to Test Step 3.

Not OK - The resistance is greater than 5 ohms. There is a problem with a connector and/or thewiring from the P1 connector.

Repair: The problem may be between the P1 connector and the J9 connector. Alternatively, theproblem may be between the P9 connector and the device that provides the 4 to 20 mAsignal.Repair the connection and/or the wire, when possible. Replace parts, if necessary. Verifythat the problem is resolved.

STOP

Test Step 3. Check for a Short Circuit to the +Battery at Terminal P1-36

A. Verify that the engine control is in the OFF/RESET mode and that the 16 amp circuit breaker isOFF.

B. Make sure that there is no electrical power to the device that provides the 4 to 20 mA signal.


22/04/2014


8/15



(P1-36) + Signal

(P1-57) +Battery

C. Use an ohmmeter to measure the resistance between terminals P1-36 and P1-57.

Expected Result:

The resistance is greater than 20,000 ohms.

Results:

Yes - The resistance is greater than 20,000 ohms. The wiring from terminal P1-36 is not shorted tothe +battery side. Do not reconnect any connectors. Proceed to Test Step 4.


22/04/2014


9/15

No - The resistance is less than 20,000 ohms. There is a problem with a connection and/or thewiring from terminal P1-36.


STOP

Test Step 4. Check for a Short to Ground at Terminal P1-37

A. Verify that the engine control is in the OFF/RESET position and that the 16 amp circuit breaker isOFF.

B. Make sure that the leads of the wires for the 4 to 20 mA signal do not create a short circuit.


22/04/2014


10/15



(1) Ground strap

(P1-37) - Signal

C. Use an ohmmeter to measure the resistance between ground strap (1) and terminal P1-37.

Expected Result:


Results:

Yes - The resistance is greater than 20,000 ohms. The wiring from terminal P1-37 appears to beOK.

Repair: Reconnect the P1 connector. Reconnect the two wires ("+" and "-") for the 4 to 20 mAsignal to the device that supplies the 4 to 20 mA signal.

Proceed to Test Step 7.

No - The resistance is less than 20,000 ohms. There is a problem with a connection and/or thewiring that is connected to P1-37.

Repair: The problem may be between the P1 connector and the J9 connector. Alternatively, theproblem may be between the P9 connector and the device that provides the 4 to 20 mAsignal.Locate the wire with the short circuit and repair the wire. Verify that the problem isresolved.

STOP

Test Step 5. Check for a Short Circuit to the +Battery Side at Terminal P1-37

A. Verify that the engine control is in the OFF/RESET mode and that the 16 amp circuit breaker isOFF.

B. Make sure that there is no electrical power to the device that provides the 4 to 20 mA signal.

C. Remove the two wires ("+" and "-") for the 4 to 20 mA signal from the device that supplies the 4to 20 mA signal. Insulate the wire leads with electrical tape in order to ensure that the leads do not

create a short circuit.

D. Disconnect the P1 connector from the master ECM.


22/04/2014


11/15



(P1-37) - Signal

(P1-57) +Battery

E. Use an ohmmeter to measure the resistance between terminals P1-37 and P1-57.

Expected Result:


Results:

Yes - The resistance is greater than 20,000 ohms. The wiring from terminal P1-37 is not shorted tothe +battery side. Do not reconnect any connectors. Proceed to Test Step 6.


22/04/2014


12/15


13/15



(1) Ground strap

(P1-36) + Signal

C. Use an ohmmeter to measure the resistance between ground strap (1) and terminal P1-36.

Expected Result:


Results:

Yes - The resistance is greater than 20,000 ohms. The wiring from terminal P1-36 appears to beOK. Do not reconnect any connectors. Proceed to Test Step 7.

No - The resistance is less than 20,000 ohms. There is a problem with a connection and/or thewiring from terminal P1-36.


STOP

Test Step 7. Check the Device that Provides the 4 to 20 mA Signal

Measure the 4 to 20 mA signal according to the literature that is provided by the OEM of the device thatprovides the 4 to 20 mA signal. Verify that the correct signal is provided to the master ECM.


22/04/2014


14/15


Harness side of the master ECM P1 connector

(P1-36) + Signal

(P1-37) - Signal

Verify the correct 4 to 20 mA signal at terminals P1-36 and P1-37.

Expected Result:

The correct 4 to 20 mA signal is provided to the master ECM.

Results:

Yes - The correct 4 to 20 mA signal is provided to the master ECM. However, the ECM is notresponding correctly to the signal. There may be a problem with the master ECM.


22/04/2014


15/15

Repair: It is unlikely that the master ECM is faulty. Exit this procedure and perform thisprocedure again. If the problem is not resolved, replace the master ECM according toTroubleshooting, "Replacing the ECM". Verify that the problem is resolved.

STOP

No - The master ECM is not receiving the correct 4 to 20 mA signal. There is probably a problemwith the device that provides the 4 to 20 mA.

Repair: Service the device that provides the 4 to 20 mA according to the literature that isprovided by the OEM of the device. Verify that the problem is resolved.

STOP

Copyright 1993 - 2014 Caterpillar Inc.

All Rights Reserved.

Private Network For SIS Licensees.

Tue Apr 22 18:48:11 UTC-0400 2014


Documents

Desired Speed Input (4 - 20 MA)