U0121 — Lost Communication With ABS Control Module
NetworkmediumThe ABS computer stopped sending messages on the data wires.
Symptoms
- ABS, traction and brake lights on
- Speedometer not working (many cars get speed from ABS)
- Cruise control off
Common causes
- ABS fuse blown
- ABS connector loose or rusty
- CAN wire fault
- ABS module faulty
How to fix
- Check ABS fuses (often two: motor and module)
- Check the ABS connector near the brake pipes
- Check CAN wires to ABS
- Scan the ABS module directly
Can I keep driving?
Normal brakes work, but ABS is off. Drive carefully.
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