AD30 and AD55 Underground Articulated Trucks Power Train Electronic Control System Caterpillar

Illustration 1	g01056589
Schematic of the backup alarm relay

This diagnostic code is associated with the backup alarm relay. This diagnostic code is recorded when the Power Train/Chassis Electronic Control Module (ECM) has determined that the voltage of the relay circuit is above normal.

The possible causes of the diagnostic code are listed:

• The relay has failed.

• The relay circuit is shorted to the +battery circuit.

• The ECM has failed. This is unlikely.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 0144 FMI 03 is active before performing this procedure.

Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure. The approximate coil resistance of the relay is 360 ohms at 25 °C (77 °F).

System Response:

The backup alarm will remain on.

Test Step 1. CHECK THE SIGNAL CIRCUIT OF THE RELAY FOR A SHORT.

1. Turn the key start switch and the battery disconnect switch to the OFF position.

2. Disconnect the machine harness from the relay.

3. Disconnect the machine harness connectors J1 and J2 from the ECM.

4. At the J1 and J2 machine harness connectors for the ECM, measure the resistance from the signal contact of the relay J2-37 (wire 321-BR(Brown)) to +battery.

Expected Result:

Each resistance should be greater than 5 ohms.

Results:

• YES - The machine harness is correct. Proceed to Test Step 2.

• NO - There is a short in the machine harness. The short is between the signal contact of the relay and the circuit with the low resistance measurement.

  Repair: Repair the machine harness or replace the machine harness.

  STOP

Test Step 2. CHECK IF THE DIAGNOSTIC CODE REMAINS.

1. Inspect the contacts and clean the contacts of the harness connectors.

2. Reconnect all harness connectors.

3. Turn the battery disconnect switch and the key start switch to the ON position.

4. Operate the machine.

5. Check the status of the CID 0144 FMI 03.

Expected Result:

The CID 0144 FMI 03 is active.

Results:

• YES - The CID 0144 FMI 03 is active. The diagnostic code has not been corrected. The ECM may have failed.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Refer to Systems operation, Troubleshooting, Testing and Adjusting, "Electronic Control Module (ECM) - Replace" for the machine that is being serviced.

  STOP

• NO - The CID 0144 FMI 03 is not active. The diagnostic code does not exist at this time.

  Repair: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.

  STOP