450E Backhoe Loader Machine Electronic Control System MID 039 - CID 0629 - FMI 04 Caterpillar

Conditions Which Generate This Code:

Illustration 1	g01217446
Schematic of the Neutralizer Switch

This diagnostic code is recorded when the ECM reads the signal voltage of the pressure switch as being too low.

The possible causes of this diagnostic code are listed:

• Wire (766-GN) is shorted to ground.

• The switch has failed.

• The ECM may have failed.

Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.

Test Step 1. CHECK THE SWITCH.

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

2. Ensure that the diagnostic code is active.

3. Observe the status of the diagnostic code. Disconnect the machine harness from the switch.

Expected Result:

The diagnostic code will remain active if the switch is not the cause of the problem. The switch is the cause of the problem if the diagnostic code is NO longer active.

Results:

• OK - The diagnostic code remains active. The switch has not failed. The machine harness may have failed or the ECM may have failed. Proceed to test step 2.

• NOT OK - The diagnostic code is NO longer active.

  Repair: The machine harness and the ECM are operating properly. The switch has failed. Replace the switch.

  STOP

Test Step 2. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND.

1. The switch remains disconnected from the machine harness.

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

3. Disconnect the machine harness connector J1 and J2 from the ECM.

4. At the J1 machine harness connector, measure the resistance from contact J2-54 (wire 766-GN) to all source of ground.

Expected Result:

The resistance should be greater than 5 ohms.

Results:

• OK - The resistance is greater than 5 ohms. The machine harness is correct. Proceed to test step 3.

• NOT OK - The resistance is less than 5 ohms.

  Repair: There is a short in the machine harness. The short is between the signal circuit (wire 766-GN) and the circuit with the low resistance measurement. Repair the machine harness or replace the machine harness.

  STOP

Test Step 3. CHECK IF THE DIAGNOSTIC CODE REMAINS.

1. Clean the contacts of the harness connectors.

2. Reconnect all harness connectors.

3. Observe the status of the diagnostic code.

4. Operate the machine.

5. Observe the status of the diagnostic code.

Expected Result:

The diagnostic code is NO longer active.

Results:

• YES - The diagnostic code is NO longer active. 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. Resume normal machine operation.STOP

• NO - The diagnostic code has not been corrected. The ECM may have failed.

  Repair: Prior to replacing an ECM, always contact your dealership Technical Communicator for possible consultation with AVSpare. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP