773G and 775G Quarry Trucks Chassis Electronic Control System Caterpillar

Illustration 1	g02665716
Schematic of the Cat data link circuit

This diagnostic code is recorded when the chassis electronic control module (ECM) does not receive expected information. For example, engine speed or actual gear information is not received from other electronic control modules through the Cat data link. This diagnostic code causes the readouts that are dependent upon the Cat data link information to indicate abnormal values.

The possible causes of this diagnostic code are listed below:

• A poor electrical connection at a machine harness connector

• A circuit in the Cat data link is shorted to ground.

• The Cat data link circuit in the machine harness is shorted to the +battery circuit.

• The Cat data link circuit in the machine harness is open.

System Response:

Diagnostic codes for the related electronic control modules are present.

Test Step 1. CHECK FOR OTHER CODES

1. Check for similar diagnostic codes that are logged against other electronic control modules.

2. If a similar diagnostic code is found, exit this test and perform the corresponding procedure for the other diagnostic code that is shown.

Expected Result:

Another diagnostic code is showing.

Results:

• OK - Exit this procedure and perform the diagnostic procedure for the diagnostic codes that are shown. STOP

• NOT OK - There are no other related diagnostic codes. Proceed to Test Step 2.

Test Step 2. INSPECT THE HARNESS CONNECTORS

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

2. Turn the disconnect switch to the OFF position.

3. Inspect the connections of the machine harness that are related to the Cat data link. Verify the following:
   • Connectors are clean.

   • Connectors are tight.

Expected Result:

The machine harness is correct.

Results:

• OK - The machine harness is correct. Proceed to Test Step 3.

• NOT OK - The machine harness is not correct.

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

  STOP

Test Step 3. CHECK FOR A SHORT TO GROUND

1. The key start switch and the disconnect switch remain in the OFF position.

2. Disconnect the machine harness from all the electronic control modules that use the Cat data link.

3. At the machine harness for the chassis ECM, measure the resistance between frame ground and connector contacts J1-10 (wire 893-GN) and J1-20 (wire 892-BR) of the Cat data link circuit.

Expected Result:

The resistance measurement should be greater than 5000 ohms.

Results:

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

• NOT OK - The resistance is less than 5000 ohms.

  Repair: The machine harness has failed. 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 key start switch and the disconnect switch remain in the OFF position.

2. All related 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 the +battery connector contact J1-31 (wire 126-RD) and connector contact J1-10 (wire 893-GN).

   • Measure the resistance between +battery connector contact J1-31 (wire 126-RD) and connector contact J1-20 (wire 892-BR).

Expected Result:

The resistance is greater than 5000 ohms.

Results:

• OK - The resistance is greater than 5000 ohms. The harness circuit resistance is correct. Proceed to Test Step 5.

• NOT OK - The resistance is less than 5000 ohms.

  Repair: The harness has failed. There is a short between the +battery contact 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 AN OPEN HARNESS

1. The key start switch and the disconnect switch remain in the OFF position.

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

3. Check the continuity of the Cat data link circuit in the machine harness.

4. At the machine harness for the chassis ECM, measure the resistance between the connector contacts J1-10 (wire 893-GN) and J1-20 (wire 892-BR) of the chassis ECM. Measure the resistance of the corresponding contacts of each electronic control module.

Expected Result:

The resistance measurement is less than 5 ohms.

Results:

• OK - The resistance measurement is less than 5 ohms.

  Repair: The Cat data link circuit in the machine harness is correct. The ECM may have failed. A failure of the ECM is unlikely. Exit this procedure and perform this procedure again. Prior to replacing an ECM, always contact the Technical communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to the Testing and Adjusting, "Electronic Control Module (ECM) - Replace" Section of this manual.

  STOP

• NOT OK - The resistance is greater than 5 ohms.

  Repair: The machine harness has failed. The Cat data link circuit is open in the machine harness. Repair the machine harness or replace the machine harness.

  STOP