Question 1

What does U0121 mean?

Accepted Answer

U0121 - Lost Communication with ABS Control Module. Vehicle lost communication with the ABS module.

Question 2

What are the symptoms of U0121?

Accepted Answer

ABS light, Traction control light, Stability control light, ABS non-functional

Question 3

What causes U0121?

Accepted Answer

ABS module failure, CAN bus wiring to ABS, ABS fuse blown, ABS connector corrosion, Water damage

Question 4

How much does it cost to fix U0121?

Accepted Answer

Typical repair cost: $100-$1,500. Check ABS fuses first. ABS module is often in a low, exposed location where water and salt cause corrosion.

U0121 — Lost Communication with ABS Control Module

Don't guess — diagnose U0121 the right way