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

The ECU detects the following condition:

• The signal from the keyswitch was rapidly cycled at least three times within the last second.

• The diagnostic trouble codes of SPN 168 FMI 4 and SPN 168 FMI 3 are not active.

• The transmission output speed is greater than 0.

The possible causes of this diagnostic code are listed:

• The keyswitch is rapidly cycled.

• The switch for the starter interlock is the engaged too long.

• The contact J2-1 has received battery power for longer than ninety seconds.

Note: This diagnostic trouble code can be generated by rapidly cycling the keyswitch. Some control units on the application may require this action in order to prompt flash codes. If this occurs, clear the logged diagnostic trouble codes in order to prevent future confusion or an incorrect diagnosis.

Note: This diagnostic trouble code can be generated when the starter interlock switch is engaged too long. Turn the switch to the off position in order to clear the diagnostic trouble code. The keyswitch may need cycled in order to clear the diagnostic trouble code.

Note: This diagnostic trouble code can be generated when battery voltage is connected to contact J2-1 for more than 1 minute.

System Response:

The ECU will log the diagnostic trouble code and the warning lamp will come on while this diagnostic trouble code is active.

Test Step 1. CHECK THE HARNESS FOR AN OPEN CIRCUIT.

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

2. Disconnect the J1 connector and the J2 connector from the Transmission ECU.

3. Disconnect the key start switch from the machine harness connector.

4. At the machine harness connector for the keyswitch, place a jumper wire between contact 3 and contact 1.

5. Use a multimeter to measure the resistance from contact J1-1 to contact J2-1.

Expected Result:

The resistance is less than 5 ohms.

Results:

• YES - The resistance is less than 5 ohms. The circuit is correct. Proceed to Test Step 2.

• NO - The resistance measurement is greater than 5 ohms. The wiring harness is not correct. A poor connection exists or an open circuit exists in the wiring harness.

  Repair: Perform the test for a poor connection. See Testing and Adjusting, "Electrical Connector - Inspect" for more information. Check the wiring harness for an open circuit. See Testing and Adjusting, "Wiring Harness (Open Circuit) - Test." for more information.

  STOP

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

1. Remove the jumper wire that was installed in the previous Test Step.

2. Measure the resistance from contact J1-1 to all of the contacts in the machine harness connector and to frame ground.

3. Note the resistance measurement.

4. Measure the resistance from contact J2-1 to all of the contacts in the machine harness connector and to frame ground.

5. Note the resistance measurement.

Expected Result:

The resistance is greater than 5000 ohms for both measurements.

Results:

• YES - The resistance is greater than 5000 ohms for both measurements. Proceed to Test Step 3.

• NO - The resistance measurement is less than 5000 ohms. The circuit with the low resistance measurement has a short.

  Repair: The circuit with the low resistance measurement has a short. Repair the wiring harness. See Testing and Adjusting, "Wiring Harness (Short Circuit) - Test." for more information.

  STOP

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

1. At the machine harness connector for the ECU, insert a multimeter probe in contact J2-1.

2. Measure the resistance from J2-1 to all possible sources of positive voltage.

Expected Result:

The resistance measurement is less than 5 ohms.

Results:

• YES - The resistance measurement is less than 5 ohms. The circuit is shorted to positive voltage. The circuit is not correct.

  Repair: Repair the circuit with the low resistance measurement. Wire L740-BU should not be wired to the +battery. Repair the machine harness or replace the machine harness. See Testing and Adjusting, "Wiring Harness (Short Circuit) - Test." for more information.

  STOP

• NO - The resistance measurement is greater than 5 ohms. The circuit is correct. Proceed to Test Step 4.

Test Step 4. 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.

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

5. Operate the machine.

6. Determine if the SPN 158 FMI 2 is active.

Expected Result:

The SPN 158 FMI 2 is active.

Results:

• YES - The SPN 158 FMI 2 is active. The diagnostic trouble code has not been corrected.

  Repair: Check the circuit again. It is unlikely that the ECU has failed. Exit this procedure and perform this procedure again. 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 158 FMI 2 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