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

Illustration 1	g00763235
Schematic of the retarder solenoid circuit

Note: The approximate coil resistance of the solenoid is 2.2 ± .2 ohms at 25 °C (77.0 °F).

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

Note: This procedure can cause new diagnostic codes to be recorded. Ignore these created diagnostic codes. Complete the following procedure. Then clear the created diagnostic codes.

Test Step 1. CHECK THE SOLENOID.

1. Turn the disconnect switch and the key start switch to the ON position. Do not start the engine. Ensure that the diagnostic code for the solenoid is active.

2. Disconnect the machine harness from the solenoid.

3. At the machine harness connector for the solenoid that is being tested, install a jumper wire. The jumper wire should be installed from contact 1 (K744-BU) to contact 2 (E790-PK).

4. Observe the status of the diagnostic code. The diagnostic code is active or the diagnostic code is NOT active.

Expected Result:

The status of the diagnostic code is active and the status of the diagnostic code is NOT active as the jumper wire is installed and then removed.

Results:

• YES - 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 active. Proceed to test step 2.

Test Step 2. CHECK THE SIGNAL CIRCUIT OF THE SOLENOID FOR A SHORT.

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 the J1 and J2 machine harness connectors for the ECM, measure the resistance from contact J2-41 (K744-BU) to all possible sources of ground. The possible sources of ground are connectors: J1-12, J2-2, J2-12, J2-13, J2-22, J2-36, J2-46, J2-49, J2-52, J2-56, J2-59 and J2-69.

Expected Result:

The resistance that is measured is greater than 5000 ohms.

Results:

• YES - The resistance that is measured is 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 the signal contact of the solenoid and the circuit with the low resistance measurement. Repair the machine harness or replace the machine 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 disconnect switch and the key start switch to the ON position.

4. Clear all of the inactive diagnostic codes.

5. Operate the machine.

6. Stop the machine. Then place the parking brake switch in the ON position.

7. Observe the status of the diagnostic code. The diagnostic code is present or the diagnostic code is NOT present.

Expected Result:

The diagnostic code for the solenoid is NO longer present.

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 and/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 ECMhas failed. Exit this procedure and perform this diagnostic code procedure again. Recheck the status of the diagnostic code. The diagnostic code is active or the diagnostic code is NOT active. Replace the ECM if the cause is not found. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  Stop.