IT38H Integrated Toolcarrier and 938H Wheel Loader Transmission Electronic Control System Caterpillar

Illustration 1	g01447881
Schematic of Cat Data Link circuit

This failure results in codes that are logged against an ECM that is not communicating some expected information to the Transmission ECM. The Transmission ECM cannot communicate with the Engine ECM or the ECM appears to work intermittently.

Test Step 1. VERIFY THE HARDWARE AND THE SOFTWARE PART NUMBERS.

1. Verify that the following information is correct:
   • The part number of the software for the Transmission ECM

   • The part number of the software for the Engine ECM

   • The part number of the Transmission ECM

   • The part number of the Engine ECM

   Note: Consult the Business Unit that produces the product for the correct part numbers of the configuration software.

Expected Result:

All part numbers are correct.

Results:

• OK - All part numbers are correct. Proceed to test step 2.

• NOT OK - All part numbers are NOT correct. The part number of the Transmission ECM may be incorrect. The part number of the Engine ECM may be incorrect. The incorrect software for the ECM may also be installed.

  Repair: Replace the incorrect ECM with an ECM that has the correct part number. Flash the correct configuration software. See Troubleshooting, "Electronic Control Module (ECM) - Flash Program" for more information.

  STOP

Test Step 2. INSPECT THE HARNESS CONNECTIONS.

1. Turn the disconnect switch to the OFF position.

2. Inspect all harness connections that are related to the Cat Data Link. Make sure that the connectors are clean and tight.

3. Check the connectors for proper mating.

4. Check the wires at the connector.

5. Check each wire for nicks or signs of abrasion in the insulation.

6. Check for moisture at the connector.

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

8. Check each pin and each socket of the machine harness connectors.

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 3.

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

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

  STOP

Test Step 3. CHECK FOR SHORTS TO GROUND.

1. The disconnect switch remains in the OFF position.

2. Disconnect the machine harness from all electronic control modules that use the Cat Data Link.

3. At the machine harness for the Transmission ECM, measure the resistance between frame ground and connector contact J1-10 (wire 944-OR) of the Cat Data Link circuit.

4. At the machine harness for the Transmission ECM, measure the resistance between frame ground and connector contact J1-20 (wire 945-BR) of the Cat Data Link circuit.

Expected Result:

The resistances are greater than 5000 ohms.

Results:

• OK - The resistances are greater than 5000 ohms. The harness circuit resistance is correct. Proceed to test step 4.

• NOT OK - Any resistance is less than 5000 ohms. The machine harness has failed.

  Repair: There is a short between frame ground and the Cat Data Link circuit in the machine harness. Repair the machine harness or replace the machine harness.

  STOP

Test Step 4. CHECK FOR A SHORT TO THE +BATTERY CIRCUIT.

1. The disconnect switch remains in the OFF position.

2. All related electronic control modules remain disconnected from the machine harness.

3. At the machine harness connector for the Transmission ECM, perform the checks that are listed here:
   • Measure the resistance between the connector contact J1-10 (wire 944-OR) and all sources of +battery.

   • Measure the resistance between connector contact J1-20 (wire 945-BR) and all sources of +battery.

Expected Result:

The resistance is greater than 5000 ohms.

Results:

• OK - The harness circuit resistance is correct. Proceed to test step 5.

• NOT OK - The resistance is less than 5.0 ohms. The machine harness has failed.

  Repair: There is a short between the +battery circuit and the Cat Data Link circuit in the machine harness. Repair the machine harness or replace the machine harness.

  STOP

Test Step 5. CHECK FOR A OPEN HARNESS.

1. The disconnect switch remains in the OFF position.

2. All related electronic control modules remain disconnected from the machine harness.

3. Check the continuity of the Cat Data Link circuit in the machine harness:
   • Measure the resistance between connector contact J1-10 (wire 944-OR) of the Transmission ECM and connector contact J1-23 (wire 944-OR) of the Engine ECM.

   • Measure the resistance between connector contact J1-20 (wire 945-BR) of the Transmission ECM and connector contact J1-24 (wire 945-BR) of the Engine ECM.

Expected Result:

The resistance measures less than 5 ohms.

Results:

• OK - The resistance is less than 5 ohms. The Cat Data Link circuit in the machine harness is correct. Proceed to test step 6.

• NOT OK - The resistance is greater than 5 Ohms. The machine harness has failed.

  Repair: The Cat Data Link circuit is open in the machine harness. Repair the machine harness or replace the machine harness.

  STOP

Test Step 6. CHECK FOR ADDITIONAL DIAGNOSTIC CODES FOR THE OTHER ELECTRONIC CONTROL MODULES.

1. Reconnect all the electronic control modules that use the Cat Data Link.

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

3. After each of the electronic control modules has been reconnected, check the Event List for diagnostic codes that are logged against the electronic control module.

Expected Result:

Diagnostic codes are not present for the other electronic control modules (ECM) in the event list.

Results:

• OK - Diagnostic codes are NOT present for the other electronic control modules.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. Check all of the connections of the data link. Make sure that the connections are clean and secure. If the cause of the diagnostic code is not found, the Engine ECM may have failed. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to Troubleshooting, "Electronic Control Module (ECM) - Replace".

  STOP

• NOT OK - Diagnostic codes are present for the other electronic control modules.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. Check all of the connections of the data link. Make sure that the connections are clean and secure. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to Troubleshooting, "Electronic Control Module (ECM) - Replace".

  STOP