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Audi A4 B8 Error Code U0121: Diagnosis and Fix Guide

Model: Audi a4 b8 Fault Code: U0121 Posted: 2018-01-12 04:44

Hi everyone! I'm experiencing issues with my Audi A4 B8, which started yesterday. Today I checked the error codes and found U0121. Can anyone please explain what this code means and how to fix it? Thank you in advance — sorry for any grammar or language mistakes! This error is commonly linked to power loss or ground faults within the ABS system. The most likely cause is a broken wire or poor connection, especially at specific pins of the ABS module.

Related fault codes

U0121

Comments (2)

Anonymous 2018-01-12 12:56

The most common issue with Audi A4 B8 U0120/U0121 is a loss of power or ground fault in the ABS system. Start by checking all fuses related to the ABS module. Then inspect all grounding points for the ABS module. Locate the ground connection points on your vehicle and ensure they are clean, tight, and properly connected. If necessary, remove the connectors, use a small wire brush, and clean both the connector and the attachment point with a baking soda and water solution. For more details: U0121 Audi A4 B8 ABS error fix

Anonymous 2018-01-13 01:58

Hi! Thanks for the reply. Yesterday I took my car to three different service centers. The final diagnosis confirmed a broken wire at pin 7 of the ABS module — this was causing no power supply. After repairing the connection, the error code cleared and the vehicle started working normally. This experience may help other Audi A4 B8 owners facing similar issues. Thanks for sharing! Have a great day!