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

The AUTO Retarder On/Off switch is connected at two inputs. The inputs are on and off. One input is open and the other input is grounded during proper operation. This diagnostic code is detected when the status of the "on" input is identical to the status of the "off" input for the AUTO Retarder ON/OFF switch.

This diagnostic code is recorded when the ARC reads the "on" circuit and the "off" circuit as having an open.

• The "on" circuit connects to connector A-A11 (wire D985-BR-16).

• The "off" circuit connects to connector A-A26 (wire D986-PK-16).

Note: Ensure that the CID 0713 FMI 03 diagnostic code is present and/or active.

Note: The following procedure can create other related diagnostic codes. The ARC detects these related diagnostic codes.

1. CHECK THE GROUND CIRCUIT OF THE HARNESS.

   1. Disconnect the A connector from the ARC.

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

   3. At the machine harness connector for the ARC, measure the resistance between contact 2 (wire 202-BK-16) and frame ground.

      Expected Result: The resistance is 2.0 ohms or less.

      Results:

      • OK: The resistance is 2.0 ohms or less. Proceed to Step 2.

      • NO: The resistance is greater than 2.0 ohms. The ground circuit for the harness is faulty. Wire (202-BK-16) has excessive resistance in the machine harness. The excessive resistance is between the switch and contact A-A2. Repair the machine harness or replace the machine harness. STOP.

2. CHECK THE SWITCH.

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

   2. Reconnect the A machine harness connector to the ARC.

   3. Place the ARC in the detected fault mode (mode 1).

   4. Ensure that the diagnostic code is present and/or active.

   5. Observe the ON/OFF status of the fault present indicator.

   6. Place a jumper between the "on" wire (D985-BR-16) of the switch to wire (202-BK-16) at the switch.

      Expected Result: The diagnostic code remains active.

      Results:

      • OK: The diagnostic code remains active. Proceed to Step 3.

      • NO: The diagnostic code changes from an active state to a not active state. The switch has failed. Repeat this test "CHECK THE SWITCH" in order to verify that the switch has failed. Replace the switch. STOP.

3. CHECK THE RESISTANCE OF THE "N/C" WIRE.

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

   2. Remove the jumper of the previous test "CHECK THE SWITCH".

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

   4. Place the ARC ON/OFF switch in the ON position.

   5. Measure the resistance between contact A-A11 (wire D985-BR-16) and the frame ground.

      Expected Result: The resistance should measure less than 5000 ohms.

      Results:

      • OK: The resistance measures less than 5000 ohms. Proceed to Step 4.

      • NO: The resistance is greater than 5000 ohms. The machine harness has failed. The "ON" harness circuit (wire D985-BR-16) is open within the machine harness. The open in the wire is between the ARC and the switch. Repair the machine harness or replace the machine harness. STOP.

4. CHECK THE RESISTANCE OF THE "N/O" WIRE.

   1. The conditions of the previous test remain intact.

   2. Place the ON/OFF switch in the OFF position.

   3. Measure the resistance between contact A-A26 (wire D986-PK-16) and the frame ground.

      Expected Result: The resistance measures less than 5000 ohms.

      Results:

      • OK: The resistance measures less than 5000 ohms. The "off" circuit (wire D986-PK-16) is correct. It is unlikely that the ARC is faulty. Exit this procedure and perform a check of the CID and the FMI again. If the cause of the diagnostic code is NOT found, replace the ARC. Testing And Adjusting, "ARC - Replace". STOP.

      • NO: The resistance is greater than 5000 ohms. The machine harness is faulty. The "off" circuit (wire D986-Pk-16) is open within the machine harness. The open is between the ARC and the switch. Repair the machine harness or replace the machine harness. STOP.