U0121 fault code: what it means

U0121: Lost communication with the ABS module. ABS and stability control are likely off.

Network (communication between modules) · Costly if missed

Usual causes, most likely first

corroded or wet ABS module connector
internal ABS module failure
blown ABS fuse or poor power feed
damaged CAN wiring

U0121 by make

MG

Lost communication with the ABS module. ABS and stability warnings may show; brakes still work without ABS.

Usual causes: ABS module power/earth fault; CAN wiring or connector; faulty ABS module

What the repair usually costs

ABS pump / control module replacement (reman exchange or new)NZ$850–NZ$3,210 · A$780–A$2,880

Not sure what U0121 means on your car? Ask Credov.

Before you clear it

Write the code down or photograph the scanner first. A code that comes straight back after clearing points to a fault that is still there. A car whose codes were cleared just before you arrived may be hiding one: the scanner's readiness monitors show "not ready" for a while after codes are cleared.

Researched by Credov from manufacturer and workshop sources. A fault code points to where a fault may be; a workshop confirms it with a diagnosis. Browse all fault codes.