CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Caterpillar

Illustration 1	g02305055
Schematic of the transfer case differential lock solenoid.

This diagnostic trouble code is associated with the transfer case differential lock solenoid The FMI 5 means that the ECU has determined that an open in the circuit exists.

The possible causes of this diagnostic trouble code are listed below:

• The energize circuit of the solenoid is open.

• The return circuit of the solenoid is open.

• The solenoid has failed.

• The ECU has failed. The ECU failing is unlikely.

Note: The following test procedure may create other diagnostic trouble codes. Ignore these created diagnostic trouble codes and clear these diagnostic trouble codes when the original diagnostic trouble code has been corrected. Ensure that the diagnostic trouble code of SPN 746 FMI 5 is active before performing this procedure.

Note: Use a digital multimeter for the measurements in this procedure.

System Response:

The solenoid will not engage.

Test Step 1. CHECK THE SOLENOID.

1. Turn the disconnect switch and the key start switch to the ON position. Do not start the engine.

2. Disconnect the solenoid with the active diagnostic trouble code from the machine harness.

3. At the machine harness connector for the solenoid, place a jumper wire from contact 1 (wire 705-PK) to contact 2 (wire 921-WH).

4. Observe the status of the SPN 746 FMI 5.

Expected Result:

The diagnostic trouble code is active. Then, the diagnostic trouble code changes from FMI 5 to FMI 6 as the jumper wire is installed.

Results:

• YES - The diagnostic trouble code remains active. The jumper wire does not affect the diagnostic trouble code. Proceed to Test Step 2.

• NO - The diagnostic trouble code is no longer active. The solenoid has failed.

  Repair: The solenoid has failed. Replace the solenoid. Verify that the new solenoid corrects the problem.

  STOP

Test Step 2. CHECK THE HARNESS FOR AN OPEN.

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

2. Disconnect the machine harness connectors from the ECU.

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

4. At the machine harness connector, measure the resistance from signal contact J1-62 (wire 705-PK) to contact J1-60 (wire 921-WH).

Expected Result:

The resistance is less than 5.0 ohms.

Results:

• OK - The resistance is less than 5.0 ohms. The machine harness is correct. Proceed to Test Step 3.

• NOT OK - The resistance is greater than 5000 ohms. The resistance measurement is not correct. There is an open circuit in the machine harness.

  Repair: Repair the machine harness or replace the machine harness.

  STOP

Test Step 3. CHECK IF THE DIAGNOSTIC TROUBLE CODE REMAINS.

1. Inspect the harness connectors. Clean the contacts of the harness connectors and check the wires for damage to the insulation that is caused by excessive heat, battery acid, or chafing.

2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit.

3. Reconnect all harness connectors in order to make sure that the connectors are fully seated. Also, make sure that the clips for each connector are fastened.

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

5. Operate the vehicle.

6. Check the status of the SPN 746 FMI 5.

Expected Result:

The SPN 746 FMI 5 is active.

Results:

• YES - The SPN 746 FMI 5 is active. The diagnostic trouble code has not been corrected.

  Repair: Check the circuit again. If the Caterpillar Electronic Technician (ET) is available, use the Cat ET service tool in order to perform a "Wiggle Test" on the machine wiring harness. The "Wiggle Test" can detect shorts and opens in the machine wiring harness that are momentary or intermittent. It is unlikely that the ECU has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic trouble code is not found, replace the ECU. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Unit - Replace".

  STOP

• NO - The SPN 746 FMI 5 is not active. The diagnostic trouble code does not exist at this time. The initial diagnostic trouble 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