Trouble codes › U0121
U0121 Lost Communication With Anti-Lock Brake System (ABS) Control Module
Network
U0121 means other modules have lost communication with the ABS module, so ABS and stability control may be off.
Another module on the network stopped hearing from the ABS module. ABS and stability control are usually turned off until communication returns.
Normal braking still works, but ABS and stability control may be off: leave extra stopping distance, especially on wet roads. Get it fixed soon.
Common causes
- A blown ABS fuse or bad ground
- A failing ABS module (some have known failures)
- Damaged wiring or a corroded connector near the ABS module
- Low battery voltage
Symptoms
- ABS and traction control lights on
- Speedometer problems on some vehicles
- Other module codes
What to check first
- Check the ABS fuses (there are often two, a large one for the pump).
- Check the ABS module's connector and ground.
- Check battery voltage.
- Check for service bulletins on your ABS module.
What does U0121 mean on your vehicle?
The likely cause depends on your engine. iRepair researches your exact year, make, model and engine (service bulletins, recalls and owner reports) and tells you what to check first. Your first 3 questions are free.
Ask iRepair about U0121No scanner? Most auto parts stores read check-engine codes for free.
Related codes
General guidance for U0121 on most vehicles. Some makers use the same code a little differently; confirm in the service information for your vehicle, put safety first, and see a professional when in doubt.