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

Illustration 1	g01257797
Schematic of the J1939 Data Link

The diagnostic trouble code is associated with the Transmission ECU. The FMI 9 means that the ECU is not receiving any of the expected information from the data link.

The possible causes of this diagnostic trouble code are listed if only two ECUs cannot communicate:

• Loose harness connections

• Open wires

• Problems with the terminating resistors

• Wires that are shorted to ground

• Wires that are shorted to the battery

• Data link high wire is shorted to the data link low wire

• High resistance across the Data Link

• Interference across the wires for the Data Link

• Incompatible Software

• Incorrect set up for parameter

• Failure of a smart device

• The ECU has failed. This is unlikely.

The possible causes of this diagnostic trouble code are listed if all of the ECUs cannot communicate:

• Problems with the terminating resistors

• Wires that are shorted to ground

• Wires that are shorted to the battery

• Data Link high wire is shorted to the Data Link low wire

• Interference across the wires for the Data Link

Note: The high and the low wires of the data link have a positive voltage. One does not have a negative voltage. The shield wire should not be used as a ground wire when the voltage is measured. Always use a clean, unpainted connection to the frame ground. The Caterpillar Electronic Technician, Cat ET, may show a controller to be off-line. The controller may not have been recognized by Cat ET. Cycling the key and restarting the Cat ET may correct the problem.

Test Step 1. INSPECT THE HARNESS CONNECTIONS.

1. Turn the disconnect switch to the OFF position.

2. Inspect all of the harness connections. Make sure that the connectors are clean and tight.

3. Check the connectors for proper mating. Ensure that all the seals are present and in place.

4. Check the harness for signs of damage or abrasion.

5. Check the wires at the connector. Ensure that the wires are secured tightly into the connector. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit. Take care not to pull the wire out of the connector.

6. Check the exposed wires at the connectors for nicks or signs of abrasion.

7. Check for moisture inside the connector.

8. Check the connectors for dirty contacts or corroded contacts.

9. Check each pin and each socket of the machine harness connectors. Ensure that the contacts are properly installed. The contacts should mate correctly when the two pieces of the connector are placed together.

Note: See Testing and Adjusting, "Electrical Connector - Inspect" for more information.

Expected Result:

The machine harness connectors are tight and free of corrosion.

Results:

• OK - The machine harness connectors are tight and free of corrosion. Proceed to Test Step 2.

• NOT OK - The machine harness connectors are in need of repair.

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

  Proceed to Test Step 8.

Test Step 2. CHECK THE VOLTAGE OF THE DATA LINK.

1. Turn the keyswitch and the disconnect switch to the ON position.

2. At the ECU, use an electrical spoon to measure the voltage. One at a time, measure the voltage of connector contact J1-67, J1-68, and J1-69 to frame ground.

   Note: Do not use the shield wire as a ground.

   Show/hide table

   Table 1

   J1-67	J1-68	J1-69
   0.5V to 4.5V	0.5V to 4.5V	0V

Expected Result:

The shield wire does not have a voltage. A voltage on the shield wire means that there is a short to the battery. The voltage of the wires for the Data Link is correct.

Results:

• OK - The voltage of the wires for the Data Link is correct. Proceed to Test Step 3.

• NOT OK - The voltage is greater than 4.5 V.

  Repair: Repair the machine harness or replace the harness.

  Proceed to Test Step 8.

• NOT OK - The voltage is less than 0.5 V. Proceed to Test Step 3.

Test Step 3. CHECK FOR A SHORT TO GROUND.

1. Turn the keyswitch and the disconnect switch to the OFF position.

2. Disconnect the J1 harness connector for the ECU. Disconnect the harness connector for the shift pad.

3. Measure the resistance of wire (K900-YL) to an unpainted frame ground. Measure the resistance of wire (K990-GN) to an unpainted frame ground.

Expected Result:

The resistance measurement is greater than 5000 ohms.

Results:

• OK - The resistance measurement is correct. Proceed to Test Step 5.

• NOT OK - The resistance measurement is not correct. The wire with the low resistance measurement is shorted to ground.

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

  Proceed to Test Step 8.

Test Step 4. CHECK FOR A SHORT IN THE WIRES FOR THE DATA LINK.

1. The keyswitch and the disconnect switch remain in the OFF position.

2. Disconnect the terminating resistors if the resistors are a part of the circuit.

3. Measure the continuity between the data link wires.

Expected Result:

The resistance measurement is greater than 5000 ohms.

Results:

• OK - The resistance measurement is correct. Proceed to Test Step 5.

• NOT OK - The resistance measurement is not correct. The wires for the data link are connected.

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

  Proceed to Test Step 8.

Test Step 5. CHECK FOR AN OPEN IN THE WIRES FOR THE DATA LINK.

1. The keyswitch and the disconnect switch remain in the OFF position.

2. Disconnect wire (K900-YL) and wire (K990-GN) from the ECU.

3. Measure the continuity of each wire individually. Use a jumper wire in order to connect to the other end of the wire in question.

Expected Result:

There is continuity from one end of the wire to the other end.

Results:

• OK - There is continuity from one end of the wire to the other end. The wire is correct. Proceed to Test Step 6.

• NOT OK - There is not continuity from one end of the wire to the other end. The wire is not correct.

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

  Proceed to Test Step 8.

Test Step 6. CHECK THE TERMINATING RESISTORS.

Note: Two 120 Ohm resistors should be located on the CAN Data Link. A resistance of 60 ohms should be found at any point on the data link. Terminating resistors are not always used on data links. The resistance measurement should be greater than 5000 ohms if resistors are not intentionally a part of the circuit.

1. The keyswitch and the disconnect switch remain in the OFF position.

2. Use an electrical spoon in order to connect to the back of the connector for one of the terminating resistors.

3. Measure the resistance between the wires.

Expected Result:

The resistance measurement is between 55 and 65 ohms.

Results:

• OK - The resistance measurement is correct. Proceed to Test Step 7.

• NOT OK - The resistance measurement is approximately 120 ohms. One of the resistors is not functioning properly.

  Repair: Ensure that the resistor is fully connected to the data link. Replace the resistor if the resistor has failed.

  Proceed to Test Step 8.

• NOT OK - The resistance measurement is approximately 40 ohms.

  Repair: There are more than two resistors on the circuit for the data link. Remove the extra resistor.

  Proceed to Test Step 8.

Test Step 7. CHECK IF THE SHIELD WIRE IS SHORTED TO GROUND.

1. The keyswitch and the disconnect switch remain in the OFF position.

2. Remove the shield wire (A249-BK) from the connector harness at the ECU for every ECU.

3. Use a multimeter in order to measure the resistance of wire (A249-BK) to an unpainted machine ground.

Expected Result:

The resistance measurement is greater than 5000 ohms.

Results:

• OK - The resistance measurement is greater than 5000 ohms. The circuit is correct. Proceed to Test Step 8.

• NOT OK - The resistance is less than 5000 ohms. The circuit is incorrect. The shield wire is shorted to ground.

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

  Proceed to Test Step 8.

Test Step 8. 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. Make sure that the harness connectors are fully seated and 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 vehicle.

6. Check the status of the SPN 639 FMI 9.

Expected Result:

The SPN 639 FMI 9 is active.

Results:

• YES - The SPN 639 FMI 9 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. 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 639 FMI 9 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 at one of the harness connectors that was disconnected and reconnected. Resume normal vehicle operation.STOP