AI DamageU0121 code: Lost Communication With Anti-Lock Brake System (ABS) Control Module A
Code U0121 is named in 41 US owner complaints, 1 of them (2%) after a crash. Models: 28, model years 2004–2024.
What the code means
Lost Communication With Anti-Lock Brake System (ABS) Control Module A. Generic meaning per SAE J2012 (the same for all makes).
How to read U0121: the letter U means network communication between modules; the second digit 0 marks a generic SAE code shared by all makes; the last three characters 121 identify the specific fault.
ABS/ESC codes: wheel speed sensors, the ABS hydraulic unit and pump, brake booster, pressure and yaw sensors. A hit to a wheel or suspension often damages the wheel speed sensor or its wiring, so on a damaged car this code is a reason to inspect the hub, knuckle and control arms, not just swap the sensor.
Key figures
- Complaints with this code
- 41
- after a crash
- 1 (2%)
- Models
- 28
- Model years
- 2004–2024
Which models and years
Models whose owners name this code (28). Years link to the model year problems page.
| Model | Years | Complaints |
|---|---|---|
| Chevrolet Malibu | 2009, 2010, 2014, 2020 | 6 |
| Ford F-150 | 2017, 2020, 2021 | 3 |
| Chevrolet Cobalt | 2006, 2007 | 2 |
| Chevrolet Traverse | 2010, 2023 | 2 |
| Dodge Charger | 2006, 2014 | 2 |
| Ford F-250 SD | 2024 | 2 |
| Jeep Wrangler | 2008, 2015 | 2 |
| Toyota RAV4 | 2006 | 2 |
| Buick Enclave | 2018 | 1 |
| Chevrolet Colorado | 2019 | 1 |
| Chevrolet Cruze | 2015 | 1 |
| Chevrolet Equinox | 2018 | 1 |
| Chevrolet Malibu ECO | 2013 | 1 |
| Chrysler 200 | 2012 | 1 |
| Dodge RAM 3500 | 2011 | 1 |
| Ford Escape Hybrid | 2020 | 1 |
| Ford Explorer | 2015 | 1 |
| Ford Focus | 2018 | 1 |
| Ford Fusion | 2014 | 1 |
| Jeep Cherokee | 2014 | 1 |
| Jeep Gladiator | 2020 | 1 |
| Jeep Liberty | 2006 | 1 |
| Mazda CX-5 | 2014 | 1 |
| Mercedes-Benz C 300 | 2017 | 1 |
| RAM 1500 | 2014 | 1 |
| Volkswagen GTI | 2009 | 1 |
| Volkswagen Jetta | 2004 | 1 |
| Volkswagen Rabbit | 2009 | 1 |
Components named together with the code
Component as the owner filed it (one complaint can list several).
Complaints by model year
What to do if an auction car has this code
- Inspect the wheel and suspension on the impact side: the wheel speed sensor is often damaged together with the hub or knuckle.
- Check whether the ABS and ESC lights stay on after start-up.
- After replacing sensors or the hydraulic unit, bleeding and scan tool adaptation may be required.
What owners report
Excerpts of owner complaints in the original wording. Owner statements not verified by the regulator; personal data removed.
I was at a complete standstill. When my mechanic evaluated it, a bunch of error codes printed out, one of which was U0121 multi-axis acceleration sensor lost communication with electronic brake control module.
Diagnostic scanning with FORScan revealed the following communication-related diagnostic trouble codes: ⢠U0131 â Lost Communication with Power Steering Control Module. ⢠U0121 â Lost Communication with Anti-Lock Brake System (ABS) Module.
The check engine, ABS, traction control, and parking brake lights all illuminated. I took the vehicle to Advance Auto for an initial code scan and had error codes U1120 (lost wheel distance), U1110 (lost vehicle speed), and U0121 (lost communication system with ABS module).
Related codes
- C0020ABS Pump Motor Control
- U0415Invalid Data Received From Anti-Lock Brake…
- U0416Invalid Data Received From Vehicle Dynamics…
- U0418Invalid Data Received From Brake System…
- C0561Vacuum Sensor A/B Correlation
- C0021Brake Booster Performance
- C0063Yaw Rate Sensor
- C0040Brake Pedal Switch A
- C006CStability System
Sources: public official US data (owner complaints) and the SAE J2012 standard. Complaints are owner statements not verified by the regulator. A code from a complaint does not replace a scan tool diagnosis. Data updated 2026-11-10.