725, 730, 735, 740 and 740 EJECTOR Articulated Trucks Power Train Electronic Control System Caterpillar

Illustration 1	g00759990
Schematic for the Lamp (Differential Lock)

Illustration 2	g00679129
(1) The lamp is located within the switch.

This diagnostic code is recorded when the circuit for the lamp (differential lock) has a short to the +battery circuit.

Service Notes: Ensure that the diagnostic code is on hold. Ensure that the "SERV CODE" indicator is ON. This diagnostic code can be active at any time when the key start switch is ON. This procedure will cause new diagnostic codes to be recorded. When the procedure is completed, clear the diagnostic codes that were caused by the procedure. The differential lock lamp is located within the differential lock switch on the shift console. Connector J2-4 of the ECM is related to this diagnostic code. The ECM activates the differential lock lamp with a +battery signal.

Test Step 1. CHECK THE DIAGNOSTIC CODE.

1. Turn the key start switch to the ON position.

2. Enter the service mode of the Caterpillar Monitoring System. Put the diagnostic code on hold.

3. Observe the ON/OFF status of the "SERV CODE " indicator. When the "SERV CODE" indicator is ON, the diagnostic code is ACTIVE. When the "SERV CODE" indicator is OFF, the diagnostic code is NOT ACTIVE.

Expected Result:

The "SERV CODE" indicator is ON. The diagnostic code is ACTIVE.

Results:

• YES - The diagnostic indicator is ON and the diagnostic code is ACTIVE. Proceed to test step 2.

• NO - The diagnostic code is NOT ACTIVE. The diagnostic code is probably intermittent. Clear the diagnostic code. Resume normal machine operation and watch for a recurrence of the diagnostic code. Stop.

Test Step 2. CHECK THE SIGNAL WIRE FOR A SHORT.

1. Turn the key start switch OFF.

2. Disconnect the machine harness connector from the ECM.

3. Check the signal circuit for a short circuit to the +battery circuit. At the machine harness connector for the ECM, measure the resistance from the +battery contact to the signal contact J2-4.

Expected Result:

The resistance is less than 5000 Ohms.

Results:

• YES - The resistance is less than 5000 Ohms. The signal circuit is shorted.

  Repair: In the machine harness, signal wire 498-WH is shorted to the +battery circuit. Repair the machine harness or replace the machine harness.

  Stop.

• NO - The resistance is greater than 5000 Ohms. The harness resistance is correct. The ECM has failed.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. Also, recheck if the "SERV CODE" indicator is illuminated for this diagnostic code. If the cause of the diagnostic code is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  Stop.