U0121 Lost Communication With ABS – Bentley

Bentley W12 code U0121 : Lost Communication With Anti-Lock Brake System (ABS) Control Module

U0121 Bentley Lost Communication With ABS : This code is concerned with the communications circuit between the Anti-Lock Brake (ABS) control module and other control modules on the vehicle. This communications circuit is most often referred to as Controller Area Network bus communications, or simply put, CAN bus. Without this CAN bus, control modules cannot exchange information, and your scan tool may not be able to communicate with the vehicle, depending on which circuit is affected.

Typically the causes for this code to set are:

• Open in the CAN bus + circuit
• Open in the CAN bus – circuit
• Short to power in either CAN bus circuit
• Short to ground in either CAN bus circuit
• Rarely – faulty control module

The Electrical Wiring Diagram of Bentley ABS below…

The location of C00822, C00769, C00748, C00754 Bentley Fuse below…

After checking the wiring circuit, power supply, GND, CAN bus if OK then replace and coding Bentley ABS Control Module.