793F Series AC Off-Highway Truck/Tractor Braking System Caterpillar

Illustration 1	g02730469
Schematic of the "Front Brake Retarder Control" solenoid

This diagnostic code is associated with the "Front Brake Retarder Control" solenoid. This diagnostic code is recorded when the Brake ECM reads the current of the solenoid as being below normal.

The possible causes are listed below:

• There is an open in the circuit.

• The solenoid has failed.

• The Brake ECM has failed. This situation 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 1607 FMI 05 is active before performing this procedure.

Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure.

System Response:

The "Front Brake Retarder Control" solenoid is always de-energized. The ECM will not be able to energize the front retarder control solenoid. The Automatic Retarder Control (ARC) will continue to operate using the rear retarder control solenoid. The ARC system will operate at a reduced level of performance.

Test Step 1. CHECK THE SOLENOID

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

2. Disconnect the machine harness from the solenoid.

3. At the machine harness connector for the solenoid, place a jumper wire from contact 1 (wire F792-WH(White)) to contact 2 (wire J815-BK(Black)).

4. Observe the status of the diagnostic code.

Expected Result:

The diagnostic code is active. Then, the diagnostic code is not active as the jumper wire is installed and removed.

Results:

• YES - The circuit is correct. The solenoid has failed.

  Repair: Repeat this test "CHECK THE SOLENOID" 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 SOLENOID CIRCUIT FOR AN OPEN

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

2. Disconnect the J1 machine harness connector from the Brake ECM.

3. At the machine harness connector for the solenoid, the jumper wire remains installed.

4. At J1 machine harness connector, measure the resistance from contact J1-54 (wire J815-BK(Black)) to J1-68 (wire F792-WH(White)).

Expected Result:

The resistance should be less than 5 ohms.

Results:

• YES - The resistance is less than 5 ohms. The machine harness is correct. Proceed to Test Step 3.

• NO - The resistance measurement is not correct. There is an open circuit in the machine harness.

  Repair: The open is in the wire for the solenoid signal or the open is in wire J815-BK(Black) of the machine harness. Repair or replace the machine harness.

  STOP

Test Step 3. CHECK IF THE DIAGNOSTIC CODE REMAINS

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

2. Reconnect all the 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 1607 FMI 05 diagnostic code.

Expected Result:

The CID 1607 FMI 05 diagnostic code is active.

Results:

• YES - The CID 1607 FMI 05 diagnostic code is active. The diagnostic code has not been corrected. The Brake ECM may have failed.

  Repair: A failure of the Brake ECM is unlikely. Exit this procedure and perform this procedure again. Prior to replacing an ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - The CID 1607 FMI 05 diagnostic code 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. Resume normal machine operation.

  STOP