OBD-II Code · Network
U0121
Lost Communication With ABS Module
high severitySafe to drive$200-$1,800
Other modules cannot reach the ABS module.
Common symptoms
- ABS + brake warning lights
- Speedo erratic in some designs
Likely causes
- ABS module unpowered
- CAN wiring
- Failed ABS module
Where to start
- Try the cheapest cause first. Start by checking: abs module unpowered.
- Cost & scope. $200-$1,800
- If the code returns after the fix: escalate to a shop or scanner with live-data and freeze-frame. A code that re-sets means the underlying fault is still there.
Related codes
P0600Serial Communication LinkU0001High Speed CAN Communication BusU0002High Speed CAN Communication Bus PerformanceU0010Medium Speed CAN Communication BusU0073Control Module Communication Bus A OffU0076Control Module Communication Bus B OffU0100Lost Communication with ECM/PCMU0101Lost Communication with TCM
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