U0121

U0121-LOST COMMUNICATION WITH ANTI-LOCK BRAKE MODULE







- When Monitored:
With the ignition on.

Battery voltage between 10 and 16 volts.

IOD fuse installed.

Totally Integrated Power Module (TIPM) is configured correctly.

- Set Condition:
Bus messages not received from the Anti-Lock Brake Module for approximately 2 to 5 seconds.





1. VERIFY THE DIAGNOSTIC TROUBLE CODE (DTC) IS ACTIVE

NOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.

1. With the scan tool, read active DTCs.

Is this DTC active?

Yes

- Go To 2

No

- Perform the STORED LOST COMMUNICATION DTCS test procedure. Stored Lost Communication DTCs.

2. CHECK FOR ANY OF THE FOLLOWING ACTIVE DTCS
1. With the scan tool, read all active DTCs from all modules.

NOTE: Check for TIPM configuration, CAN B or C hardware electrical, VIN Missing/Mismatch, battery or ignition related DTCs.

Does the scan tool display any active DTCs to the conditions listed above?

Yes

- Go to and perform the appropriate diagnostic procedure.

No

- Go To 3

3. VERIFY THAT THE ABS IS ACTIVE ON THE BUS
1. Turn the ignition on.
2. With the scan tool, select Network Diagnostics.
3. Verify that the ABS is active on the bus.

Is the ABS active on the bus?

Yes

- Go To 4

No

- Perform the NO RESPONSE FROM ABS (ANTILOCK BRAKE MODULE) diagnostic procedure. No Response From ABS (Antilock Brake Module).

4. CHECK FOR ADDITIONAL COMMUNICATION RELATED DTCS
1. With the scan tool, select Network Diagnostics.

Is there more than one module with active DTCs "Logged Against" the ABS?

Yes

- Replace/update the Anti-Lock Brake Module.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.

No

- Replace/update the module that set this DTC
- Perform the appropriate VERIFICATION TEST Verification Tests.