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

Illustration 1	g00762287
Schematic of the Cross Axle Differential Lock Solenoid Valve

This diagnostic code is recorded when the ECM reads the current of the solenoid circuit as above normal (short to ground).

The possible causes for this diagnostic code are listed:

• The circuit of the solenoid is shorted to ground.

• The solenoid has failed.

• The ECM has failed. This is unlikely.

The nominal resistance of the coil at room temperature is 34 ohms.

Test Step 1. CHECK THE SOLENOID.

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

2. Ensure that the diagnostic code for the solenoid is on hold.

3. Observe the status of the "SERV CODE" indicator.

4. Disconnect the machine harness from the solenoid.

Expected Result:

The "SERV CODE" is no longer showing when the solenoid is disconnected.

Results:

• YES - The "SERV CODE" is no longer showing when the solenoid is disconnected. The circuit is correct. The solenoid has failed.

  Repair: Repeat this test step "CHECK THE SOLENOID" in order to verify that the solenoid has failed. Replace the solenoid.

  Stop.

• NO - The diagnostic code remains. Proceed to test step 2.

Test Step 2. CHECK THE SOLENOID CIRCUIT FOR A SHORT TO GROUND.

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

2. Disconnect the machine harness from the solenoid.

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

4. At machine harness connector J1 and J2, measure the resistance from the signal contact J2-25 (wire 368-OR) to all possible sources of ground. The possible sources of ground are contacts: 725 and 730 machines J1-12, J2-2, J2-12, J2-13, J2-22, J2-36, J2-41, J2-46, J2-49, J2-52, J2-56, J2-59 and J2-69. 735 machines J1-12, J1-20, J2-2, J2-12, J2-13, J2-18, J2-22, J2-36, J2-46, J2-49, J2-52, J2-56, J2-59 and J2-69. 740 machines J1-12, J1-20, J2-2, J2-12, J2-13, J2-22, J2-36, J2-46, J2-56, J2-59 and J2-69.

Expected Result:

The resistance should be greater than 5000 ohms for each measurement.

Results:

• YES - The resistance measurements were greater than 5000 ohms. The machine harness is correct. Proceed to test step 3.

• NO - The resistance is less than 5000 ohms. There is a short in the machine harness.

  Repair: The short is between wire (368-OR) and the circuit with the low resistance measurement. Repair the harness or replace the harness.

  Stop.

Test Step 3. 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 key start switch and the disconnect switch to the ON position.

4. Enter service mode of the Caterpillar Monitoring System and clear all inactive diagnostic codes.

5. Operate the machine.

6. Observe the status of the diagnostic code for the solenoid. The "SERV CODE" is NOT showing.

Expected Result:

The diagnostic code for the solenoid is NOT present. The "SERV CODE" is NOT showing.

Results:

• YES - The diagnostic code is NOT present. The diagnostic code does not exist at this time. 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.

• NO - The diagnostic code has not been corrected. The ECM has failed.

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

  Stop.