AD45B Underground Articulated Truck Power Train Electronic Control System Caterpillar

Illustration 1	g01155539
Schematic of the rear service brake and retarder pressure switch

This diagnostic code is associated with the rear service brake and retarder pressure switch. This diagnostic code is recorded when the Power Train/Chassis Electronic Control Module (ECM) reads the voltage of the switch as being above normal.

The possible causes of this diagnostic code are listed:

• Wire K992-PU shorted to the +battery.

• The switch has failed.

• Wire K992-PU or 202-BK is open.

• The ECM has failed. This 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 1640 FMI 03 is active before performing this procedure.

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

System Response:

Before the ECM determines that a diagnostic code exists, the machine will be difficult to upshift. The ECM will default to the shift points for the retarding shift map. When the ECM determines that a diagnostic code exists, the ECM will default to the shift points for the non-retarding shift map.

Test Step 1. CHECK THE SWITCH

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

2. Ensure that the diagnostic code is active.

3. At the machine harness connector for the switch place a jumper wire from contact 1 (wire K992-PU) to contact 2 (wire 202-BK).

4. 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 the jumper wire is removed.

Expected Result:

If the switch is not the cause of the diagnostic code, the diagnostic code remains active. If the switch has failed, the diagnostic remains not active.

Results:

• OK - The diagnostic code remains active the switch has not failed. Proceed to Test Step 2.

• NOT OK - The diagnostic changes from an active state to a inactive state. The switch has failed.

  Repair: Repeat this test "CHECK THE SWITCH" in order to verify that the switch has failed. Replace the switch.

  Stop.

Test Step 2. CHECK FOR AN OPEN CIRCUIT

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

2. Disconnect the J1 and J2 machine harness connectors from the ECM.

3. The jumper wire that was installed in the previous Test Step remains in place.

4. At the J2 machine harness connector for the ECM, measure the resistance from the signal contact J2-45 (wire K992-PU) to frame ground.

Expected Result:

The resistance that is measured is less than 5 ohms.

Results:

• OK - The resistance that is measured is less than 5 ohms. Proceed to Test Step 3.

• NOT OK - The resistance measurements is greater than 5 ohms. There is an open in the machine harness.

  Repair: Repair the machine harness or replace the machine harness. Verify that the diagnostic code is no longer active.

  Stop.

Test Step 3. CHECK FOR A SHORT TO THE +BATTERY CIRCUIT

1. The key start switch and the battery disconnect switch remain in the OFF position.

2. Remove the jumper wire that was previously installed.

3. The J1 and J2 machine harness connectors remain disconnected from the ECM.

4. At the J2 machine harness connector for the ECM, measure the resistance from the signal contact J2-45 (wire K992-PU) to all possible sources of +battery.

Expected Result:

The resistance for each measurement should be greater than 5 ohms.

Results:

• OK - Each resistance measurement is greater than 5 ohms. The harness is correct. The ECM may have failed. Proceed to Test Step 4.

• NOT OK - Each resistance measurement is not greater than 5 ohms. The machine harness has failed.

  Repair: There is a short in the machine harness. The short is between the signal (wire K992-PU) and the wire with the low resistance measurement. Repair the machine harness or replace the machine harness.

  Stop.

Test Step 4. 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 1640 FMI 03.

Expected Result:

The CID 1640 FMI 03 is active.

Results:

• OK - The CID 1640 FMI 03 is active. The diagnostic code has not been corrected. The ECM may have failed.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Refer to Systems operation, Troubleshooting, Testing and Adjusting, "Electronic Control Module (ECM) - Replace" for the machine that is being serviced.

  Stop.

• NOT OK - The CID 1640 FMI 03 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 that was disconnected and reconnected. Resume normal machine operation.

  Stop.