U0121 — Lost Communication With Anti-Lock Brake System (ABS) Control Module
Category: Network / Communication Severity: High
Updated:
DTC code U0121 means: Lost Communication With Anti-Lock Brake System (ABS) Control Module. It falls under the "Network / Communication" category, with an estimated severity of High. Common causes include failed ABS module (typical solder-joint fault), blown ABS fuse and corroded ABS connector; it's worth confirming the diagnosis before replacing parts.
Possible causes
- Failed ABS module (typical solder-joint fault)
- Blown ABS fuse
- Corroded ABS connector
- Damaged CAN wiring
Symptoms
- ABS and stability lights on
- Speedometer not working
- ABS disabled
- Check engine light
How to diagnose it step by step
- Check the ABS fuses.
- Check module power and ground.
- Inspect the ABS connector.
- Try to communicate with the module.
- Repair or replace the module.
How to fix it
Check the ABS fuses (usually two: pump and module) and the hydraulic unit connector. If they're fine, the module usually needs repair or replacement.
Estimated repair cost
ABS module repair: $200–500. New module: $700–2,000.
Frequently asked questions
What does DTC code U0121 mean?
Lost Communication With Anti-Lock Brake System (ABS) Control Module.
Is code U0121 serious?
Severity High. Have it checked as soon as possible, especially if it affects safety or the catalytic converter.
Can I keep driving with code U0121?
Brakes still work, but without ABS or stability control: drive carefully, especially in the wet.
Related codes
U0140 U0101 U0100 U0151 U0155 U0164
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