793F CMD Off-Highway Truck Caterpillar

Illustration 1	g02792319
Data-link circuit

An abnormal update rate on the proprietary CAN data-link will cause this diagnostic code. An abnormal rate can be caused by the following:

• Failed propitiatory CAN data-link

• Failed propitiatory CAN data-link device

• Incorrectly connected connector

Test Step 1. INSPECT THE HARNESS

1. Turn off the keyswitch.

2. Turn off the battery disconnect switch.

3. Inspect the harness for the following:

   1. Inspect the connectors, pins, and sockets for the following:

      • Cleanliness

      • Security

      • Proper mating

      • Seal condition

      • Moisture

      • Corrosion

      • Connector allen head screw for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in)

   2. Inspect the wires at the connector for the following:

      • Security

      • Nicks

      • Abrasion

      Note: Take care not to pull the wire out of the connector.

   3. Inspect the harness for the following:

      • Damage

      • Abrasion

      • Kinks

Expected Result:

The harness is in good condition.

Results:

• OK - The harness is in good condition. Proceed to Test Step 2.

• NOT OK - The harness is not in good condition.

  Repair: Repair or replace the harness.

  STOP

Test Step 2. CHECK IF THE DIAGNOSTIC CODE REMAINS

1. Connect the Cat® ET service tool to the service tool connector.

2. Turn on the battery disconnect switch.

3. Turn on the keyswitch.

4. Check Cat ET for an active CID 0246 - FMI 09 diagnostic code.

Expected Result:

CID 0246 - FMI 09 is not active.

Results:

• OK - CID 0246 - FMI 09 is not active.

  Repair: Reset the system and troubleshoot any active diagnostic codes.

  STOP

• NOT OK - CID 0246 - FMI 09 is active. Proceed to Test Step 3.

Test Step 3. CHECK THE HARNESS RESISTANCE

1. Turn off the keyswitch.

2. Disconnect the ECM from the harness.

3. Disconnect Cat ET from the service tool connector.

4. Disconnect the attachment connector.

5. Use a jumper wire to short contact 2 and 3 together at the attachment connector.

6. Measure the resistance at the ECM connector between 27 and 35.

7. Remove the jumper wire.

Expected Result:

The resistance is low.

Results:

• OK - The resistance is low. Proceed to Test Step 4.

• NOT OK - The resistance is high or open.

  Repair: Repair or replace the harness.

  STOP

Test Step 4. CHECK THE CAN DATA-LINK FOR A SHORT

1. Measure the resistance at the attachment connector between:

   1. Pin 4 and frame ground

   2. Pin 5 and frame ground

Expected Result:

The resistance should be high or open

Results:

• OK - The resistance is high or open

  Repair: Reset the system and troubleshoot any active diagnostic codes. If the original condition still exists, the problem may be in an attached device. See the manual for the device in question.

  STOP

• NOT OK - The data-link is shorted.

  Repair: Repair or replace the harness.

  STOP