Causes and Fixes U0121 Code: Lost Communication with Anti-Lock Braking System (ABS) Module

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Added 1 year ago by vindheim

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How to fix U0121 Code: Lost Communication with Anti-Lock Braking System (ABS) Module

A U0121 means that the vehicle CAN Bus can’t communicate with the
Anti-Lock Braking System (ABS) Module.
The CAN (Controller Area Network) is a protocol that allows the ECM, PCM, TCM, and ABS modules to communicate with each other.

Symptoms of a U0121 Code:
Warning lights (ABS ESP BAS Lights)
ABS performance issues

Possible Causes of a U0121 Code:
Blown Fuse
Issues with Alternator Charging or Battery
Faulty ABS control module
Wiring such as damaged wires or poor connections

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