U0121-LOST COMMUNICATION WITH ANTI-LOCK BRAKE SYSTEM (ABS) CONTROL MODULE
For a complete wiring diagram Refer to Section 8W.
- When Monitored:
- With the ignition on
- Battery voltage between 10 and 16 volts
- IOD fuse installed
- Set Condition:
Bus messages not received from the Antilock Brake Module for approximately 500ms.
| Possible Causes |
| CAN C BUS CIRCUITS OPEN OR SHORTED |
| DTCS RELATED TO BATTERY VOLTAGE, IGNITION, OR VIN MESSAGES |
| ANTILOCK BRAKE MODULE |
| ANTILOCK BRAKE MODULE POWER AND GROUND |
| MODULE THAT SET THIS DTC |
Diagnostic Test
1.VERIFY DTC IS ACTIVENOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.
Is this DTC active?
Yes
- Go To 2
No
- Perform the Stored Lost Communication test procedure. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - DIAGNOSIS AND TESTING)
2.CHECK FOR ANY OF THE FOLLOWING ACTIVE DTCS
NOTE: Check for CAN 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
- Diagnose and repair the DTC. Refer to the Table of Contents for a complete list of the symptoms.
No
- Go To 3
3.VERIFY THAT THE ABS MODULE IS ACTIVE ON THE BUS
Is the ABS active on the bus?
Yes
- Go To 4
No
- (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - DIAGNOSIS AND TESTING) for No Response diagnostic procedures.
4.CHECK FOR ADDITIONAL COMMUNICATION RELATED DTCS
Is there more than one module with active DTCs “Logged Against” the ABS?
Yes
- Replace/update the Antilock Brake Module in accordance with the service information.
- Perform BODY VERIFICATION TEST – VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE)
No
- Replace/update the module that set this DTC in accordance with the service information
- Perform BODY VERIFICATION TEST – VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE)