797 and 797B Off-Highway Truck/Tractors Braking System Caterpillar

Illustration 1	g00875930

This diagnostic code is recorded when the brake/cooling ECM does not receive expected information from the engine ECM for a period of more than five seconds.

System Response:

This failure results in events that are logged against an ECM that can not be explained. The brake/cooling ECM can not communicate with this ECM or the ECM appears to work intermittently.

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

1. Verify whether the following part numbers are correct.
   • Software part number for the brake/cooling ECM

   • Software part number for the monitoring system

Expected Result:

Consult the Business Unit that is producing the product for the correct configuration for the machine.

Results:

• OK - All part numbers are correct. Proceed to Test Step 2.

• NOT OK - All of the part number are NOT correct.

  Repair: One of the following modules may have the wrong part number and/or the software configuration is NOT correct. See Testing and Adjusting, "Electronic Control Module (ECM) - Flash Program".

  Stop.

Test Step 2. INSPECT THE HARNESS CONNECTIONS.

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

2. Inspect the harness connections that are related to the CAT data link. Make sure that the connectors are clean and tight.

3. Check the mating of the connector.

4. Check the wires at the connector.

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

6. Check for moisture at the connector.

7. Check for dirty contacts and/or corroded contacts.

8. Check each pin and check each socket.

Expected Result:

The machine harness connectors are tight and free of corrosion.

Results:

• OK - The machine harness connectors are tight and the connectors are free of corrosion. Proceed to Test Step 3.

• NOT OK - The machine harness connectors require repair.

  Repair: Repair the harness or replace the harness.

  Stop.

Test Step 3. CHECK FOR ADDITIONAL RELATED DIAGNOSTIC CODES.

1. Ensure that all electronic control modules that use the CAT data link are connected.

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

3. Acknowledge any diagnostic codes that are currently displayed on the message center.

4. Verify that NO related diagnostic codes are present.

Expected Result:

NO other diagnostic codes are present.

Results:

• OK - NO other related diagnostic codes are present. Proceed to Test Step 4.

• NOT OK - Other related diagnostic codes are present.

  Repair: Exit this procedure and perform the other related diagnostic codes. Verify that the other related diagnostic codes are NOT present. Observe the status of the CID 0296 FMI 02. If the CID 0296 FMI 02 remains, perform the diagnostic code procedure again.

  Stop.

Test Step 4. CHECK FOR SHORTS TO GROUND

1. Turn the disconnect switch and the key start switch to 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 brake/cooling ECM, measure the resistance between frame ground and the following data link circuits:
   • Contact J1-7 (wire 892-BR) and contact J1-8 (wire 893-GN)

Expected Result:

The resistance is greater than 5000 ohms.

Results:

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

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

  Repair: There is a short between frame ground and the data link circuit in the machine harness. Repair the machine harness or replace the machine harness.

  Stop.

Test Step 5. CHECK FOR A SHORT TO THE +BATTERY.

1. The disconnect switch remains in the OFF position.

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

3. At the J1 and J2 machine harness connectors for the brake/cooling ECM, measure the resistance from contact J1-7 (wire 892-BR) and contact J1-8 (wire 893-GN) to the +battery. The +battery contacts for the brake/cooling ECM are listed: J2-1, J2-23, J2-47, J2-57 and J2-70.

Expected Result:

The resistance is greater than 5000 ohms.

Results:

• OK - The resistance is greater than 5000 ohms. Proceed to Test Step 6.

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

  Repair: There is a short between the +battery and the data link circuit in the machine harness. Repair the machine harness or replace the machine harness.

  Stop.

Test Step 6. CHECK FOR AN 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 data link circuit in the machine harness.

4. Perform the following measurements:
   Show/hide table

   Table 1

   Module	Contact	Wire
   Transmission ECM	J1-7	892-BR
   Brake/cooling ECM	J1-7	892-BR

   Show/hide table

   Table 2

   Module	Contact	Wire
   Transmission ECM	J1-8	893-GN
   Brake/cooling ECM	J1-8	893-GN

Expected Result:

The resistance measures less than 5 ohms.

Results:

• OK - The resistance measures less than 5 ohms. The data link circuit is correct. The ECM may have failed.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this diagnostic code again. Replace the ECM if the cause of the diagnostic code is not found. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  Stop.

• NOT OK - The resistance that is measured is greater than 5 ohms. The machine harness has failed.

  Repair: The data link circuit is open in the machine harness. Repair the machine harness or replace the machine harness. Verify that the repair eliminates the problem.

  Stop.