Network (U)
U0121: Lost communication with ABS module
The vehicle's control system has lost communication with the ABS control module. This can affect the anti-lock braking system's performance.
Checked by a licensed car technician · last reviewed 29 September 2026
Symptoms
- ABS warning light on
- Brakes may not function optimally
- Traction control light on
Common causes
- ABS module power fault
- CAN wiring issue
- Low voltage
- Faulty ABS module
- Blown fuse
How to check it yourself
- Check ABS fuses and power
- Inspect CAN network for related codes
- Test battery voltage
- Examine wiring and connectors to ABS module
Can I keep driving?
The car can be driven, but braking performance may be affected. Drive with caution.
General guidance, not a professional inspection. Confirm faults with measurements before buying parts, and use a qualified mechanic for brakes, steering, fuel leaks, airbags, and other safety-critical work. Terms and disclaimer