768C, 769C, 769D, 772B, 773B, 773D, 776C, 777B, 777D, 784B, 785, 785B, 789, 789B, 793, 793B and 793C Off-Highway Truck/Tractors and 771C, 771D and 775D Quarry Trucks Automatic Retarder Control (ARC) System Caterpillar

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.

1. CHECK THE SOLENOID.

   1. Turn the disconnect switch and the key start switch to the ON position. DO NOT start the engine. Place the ARC in the detected fault mode (mode 1).

   2. Ensure that the CID and the FMI for the solenoid are active.

   3. Place the parking brake switch in the OFF position.

   4. Disconnect the machine harness from the control solenoid.

   5. 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 changes to being NOT active when the solenoid is disconnected.

      Results:

      • OK: The circuit is correct. The solenoid is faulty. Repeat this test "CHECK THE SOLENOID" in order to verify the solenoid failure. Replace the solenoid. STOP.

      • NO: The diagnostic code remains active. Proceed to Step 2.

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

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

   2. The machine harness remains disconnected from the solenoid.

   3. Disconnect the machine harness connectors A from the ARC.

   4. At the A machine harness connectors for the ARC, measure the resistance from the signal contact of the solenoid A-A3 (wire D988-WH-16) to the frame ground.

      Expected Result: The resistance should be greater than 5000 ohms.

      Results:

      • OK: The resistance measurement is greater than 5000 ohms. The machine harness is correct. Proceed to Step 3.

      • NO: There is a short in the machine harness. 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.

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 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 CID and the FMI. The diagnostic code is present or the diagnostic code is NOT present.

      Expected Result: The CID and the FMI for the solenoid are NO longer present.

      Results:

      • OK: 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. It is unlikely that the ARC is faulty. Exit this procedure and perform a check of the CID and the FMI again. Recheck the status of the diagnostic code. The diagnostic code is active or the diagnostic code is NOT active. If the cause of the diagnostic code is not found, replace the ARC. See Testing And Adjusting, "ARC - Replace". STOP.