U0121Severity: High
U0121 – Lost Communication With ABS Module
The vehicle can't communicate with the ABS control module over CAN.
What it means
Other modules lose communication with the ABS (anti-lock braking) control module over the data bus. ABS/ESP and speed-based functions may be disabled.
Symptoms
- ABS/ESP warning lights
- Speedometer issues
- Driver-assist systems disabled
- Check-engine light
Common causes
- CAN bus wiring fault
- ABS module power/ground issue
- Faulty ABS module
- Connector/corrosion
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Frequently asked questions
What does trouble code U0121 mean?
U0121 – Lost Communication With ABS Module. Other modules lose communication with the ABS (anti-lock braking) control module over the data bus. ABS/ESP and speed-based functions may be disabled.
Can I drive with a U0121 code?
This code is high severity. Driving for long can damage the engine; have it checked as soon as possible.