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

Illustration 1	g01238990
Schematic of the transmission shift solenoid 1

This diagnostic trouble code is associated with the transmission solenoid valve 1. The FMI "3" means that the ECU has determined that the voltage of the solenoid circuit is above normal.

The possible causes of the diagnostic trouble code are listed:

• The solenoid has failed.

• The energize circuit of the solenoid is shorted to the +battery circuit.

• The ECU has failed. An ECU failure 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 734 FMI 3 is active before performing this procedure.

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

System Response:

Only gears that are engaged by the solenoid are available. The lockup clutch is turned OFF.

Test Step 1. CHECK THE ENERGIZE CIRCUIT OF THE SOLENOID FOR A SHORT TO THE +BATTERY CIRCUIT.

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

2. Disconnect the machine harness connectors from the solenoid and the ECU.

3. At the machine harness connector for the ECU, measure the resistance from contact J1-59 (wire 751-GN) to all contacts that are used in the machine harness connectors for the ECU.

Expected Result:

Each resistance measurement is greater than 5000 ohms.

Results:

• OK - Each resistance measurement is greater than 5000 ohms. The machine harness is correct. Proceed to Test Step 2.

• NOT OK - Each resistance measurement is not greater than 5000 ohms. There is a short in the machine harness. The short is between J1-59 (751-GN) and the circuit that has a low resistance measurement.

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

  STOP

Test Step 2. CHECK IF THE DIAGNOSTIC TROUBLE CODE IS STILL ACTIVE.

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 completely.

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

5. Operate the machine.

6. Determine if the SPN 734 FMI 3 is active.

Expected Result:

The SPN 734 FMI 3 is active.

Results:

• YES - The SPN 734 FMI 3 is active. The diagnostic trouble code has not been corrected.

  Repair: Check the circuit again. An ECU failure is unlikely. 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 ECU, 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 734 FMI 3 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