U0121
Lost Communication With Anti-Lock Brake System (ABS) Control Module A
U0121 is an OBD-II diagnostic trouble code meaning: Lost Communication With Anti-Lock Brake System (ABS) Control Module A. Common causes: open or short circuit in the communication circuit, abs module malfunction. Estimated repair cost: $56–278.
Symptoms
- The ABS indicator on the dashboard is on
- Disabling the ABS system
- Disabling related systems (ESC, BAS)
- Possible errors in other systems
- Recording a fault code in the ECU memory
Causes
- Open or short circuit in the communication circuit
- ABS module malfunction
- ABS module power problems
- Corrosion or poor contact in connectors
- Software failure in the ECU or ABS module
How to Fix
- Check ABS module fuses
- Inspect the wiring harness and connectors for damage.
- Check the power and ground of the ABS module
- Read ABS module fault codes
- If necessary, replace the ABS module
Related codes
Error U0121 by Vehicle Brand
FAQ
What does the U0121 code mean?
U0121 is an OBD-II diagnostic trouble code that indicates: Lost Communication With Anti-Lock Brake System (ABS) Control Module A
What causes a U0121 error code?
The most common causes of U0121 include: Open or short circuit in the communication circuit; ABS module malfunction; ABS module power problems; Corrosion or poor contact in connectors.
How do I fix a U0121 diagnostic trouble code?
To fix U0121: Check ABS module fuses. Inspect the wiring harness and connectors for damage.. Check the power and ground of the ABS module. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with U0121?
Limited driving only, diagnose soon
How much does it cost to fix U0121?
The estimated repair cost for U0121 is $56–278. Actual cost depends on your vehicle, location, and labor rates.
See also: Russian version · NationStat