OBD codes / U0121
U0121
SeriousLost Communication With ABS Control Module
Address promptly — can worsen or affect drivability.
Likely causes
- CAN bus fault
- ABS module power/ground
- wiring
Common fixes
- inspect CAN bus
- check ABS module connector
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.