4000 - 4999: 4721

4721-ABS/ESP - CAN MESSAGE ERROR





For a complete wiring diagram consult Diagrams/Electrical Electrical Diagrams.


- When Monitored:

Continuously.

- Set Condition:

Whenever the CAN C Bus (+) or CAN C Bus (-) is open.








Diagnostic Test


1. DTC IS ACTIVE

Ignition on, engine not running.

With the scan tool, clear DTCs in the Anti-lock Brake Module.

Cycle the ignition from off to on at least 5 times, leaving the ignition on for a minimum of 90 seconds per cycle.

With the scan tool, select View DTCs in the Anti-lock Brake Module.

Does the DTC reset and/or remain active?

Yes

- Go to 2

No

- Go to 6



2. CAN C BUS DTCs SET IN BODY CONTROL MODULE (BCM)

With the scan tool, select View DTCs in the BCM.

Are there any active CAN C Bus DTCs?

Yes

- Refer to ELECTRONIC CONTROL MODULES for diagnostic procedures and for further possible causes.

No

- Go to 3
-



3. CAN C BUS (+) CIRCUIT OPEN





Turn the ignition off.

Disconnect the Anti-lock Brake Module harness connector.

Disconnect the Ignition Switch harness connector.

Measure the resistance of the CAN C Bus (+) circuit between the Anti-lock Brake Module harness connector and the Ignition switch harness connector.

Is the resistance above 5.0 ohms?

Yes

- Repair the CAN C Bus (+) circuit for an open.
- Perform ABS VERIFICATION TEST. Verification Tests

No

- Go to 4



4. CAN C BUS (-) CIRCUIT OPEN





Measure the resistance of the CAN C Bus (-) circuit between the Anti-lock Brake Module harness connector and the Ignition Switch harness connector.

Is the resistance above 2.0 ohms?

Yes

- Repair the CAN C Bus (-) circuit for an open.
- Perform ABS VERIFICATION TEST. Verification Tests

No

- Go to 5



5. ANTI-LOCK BRAKE MODULE

Inspect the wiring between the Anti-lock Brake Module harness connector and the Ignition Switch harness connector. If any problems are found, repair as necessary. If no problems are found, view repair.



Repair

- Replace the Anti-lock Brake Module.
- Perform ABS VERIFICATION TEST. Verification Tests



6. INTERMITTENT CAN C BUS OFF PERFORMANCE DTC

The conditions necessary to set this DTC are not present at this time.

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.

While monitoring the scan tool data relative to this circuit, wiggle test the wiring and connectors.

Look for the data to change or for the DTC to reset during the wiggle test.

Were any problems found?

Yes

- Repair as necessary.
- Perform ABS VERIFICATION TEST. Verification Tests

No

- Test complete.