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

Illustration 1	g02730489
Schematic circuit connections for the "ARC Control" solenoid

This diagnostic code is associated with the "ARC Control" solenoid. The FMI 03 diagnostic code is recorded when the Brake ECM reads the voltage of the solenoid circuit as being above normal. The circuit is shorted to the battery circuit.

Some possible causes of the diagnostic code are listed below:

• The energized circuit of the solenoid is shorted to the +battery circuit.

• The 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 1608 FMI 03 is active before performing this procedure.

Note: Use the 146-4080Digital Multimeter for the measurement that are required in this procedure.

System Response:

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

Test Step 1. 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 connector from the solenoid. Disconnect the machine harness connectors J1 and J2 from the Brake ECM.

4. At the machine harness connector of the Brake ECM J1, measure the resistance from contact J1-67 (wire K988-WH(White)) to all J1 and J2 connector contacts.

Expected Result:

Each resistance measurement is greater than 5 ohms.

Results:

• OK - Each resistance measurement is greater than 5 ohms. The machine harness is correct. Proceed to Test Step 2.

• NOT OK - Each resistance measurement is not greater than 5 ohms. There is a short in the machine harness.

  Repair: The short is between the signal contact J1-67 (wire K988-WH(White)) and the circuit that has a low resistance measurement. Repair or replace the machine harness.

  STOP

Test Step 2. CHECK IF THE DIAGNOSTIC CODE IS STILL ACTIVE

1. Inspect the contacts of the harness connectors that are used in the solenoid circuit. Ensure that the contacts are secure. Clean all of the contacts in the harness connectors.

2. Reconnect all harness connectors.

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

4. Operate the machine.

5. Determine if the CID 1608 FMI 03 diagnostic code is active.

Expected Result:

The CID 1608 FMI 03 diagnostic code is active.

Results:

• YES - The CID 1608 FMI 03 diagnostic code is active. The Brake ECM may have failed.

  Repair: A failure of the 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 1608 FMI 03 code is not active. The problem 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