OBD codes / U0121
U0121
SeriousLost Communication With ABS Control Module
Address promptly — can worsen or affect drivability.
What this code means
U0121 — Lost Communication With ABS Control Module. This is a standardized OBD-II trouble code, but the exact fault and the right repair depend on your specific vehicle. The common causes and checks for this code are listed below; for a precise diagnosis on your year, make and model, scan the code (and note any companion codes) or run a diagnosis here.
Likely causes
- CAN bus fault
- ABS module power/ground
- wiring
Common fixes
- inspect CAN bus
- check ABS module connector
What it costs to fix
Varies by vehicle — get it diagnosed.
The repair cost for this code depends too much on your exact vehicle and the underlying cause to quote a meaningful range. Confirm the cause first so you only pay for the fix you actually need.
Diagnose U0121 for my vehicle →Frequently asked
Can I drive with U0121?
Be cautious. U0121 involves a system that can affect how the car runs or its safety, so it's best to have it diagnosed promptly rather than driving on it. Drive gently to a shop if you must, and stop if the car runs poorly or a warning light is flashing.
How much does it cost to fix U0121?
It varies too much to quote without a diagnosis — the same code can come from a cheap sensor or wiring fix or a more involved repair depending on your exact vehicle and the underlying cause. Confirm the real cause first so you only pay for the fix you actually need.
What should I do about U0121?
Scan the code to confirm it and note any companion codes, inspect the wiring and connectors for the affected component, and run a diagnosis specific to your year, make and model to pinpoint the cause before replacing parts.
Seeing U0121 on your car? Get a diagnosis specific to your exact year, make and model.
Diagnose U0121 for my vehicleGeneric OBD-II reference. Manufacturer-specific behavior varies — confirm with a scan tool and, for safety-related codes, a professional inspection.