U0121 to U0132: lost communication with brake, steering or chassis modules
A module stopped hearing from the ABS, the stability control, its yaw rate, acceleration or steering angle sensors, the tire pressure monitor, the electric park brake, the power steering or the ride height control.
SeverityHighCarrying on can cause expensive damage, so deal with it now.
Can you keep driving?Only as far as the workshopWhat does U0121 mean?
These modules share data that other systems rely on: the ABS module reports wheel speeds that the engine, the gearbox and the speedometer may use, and the steering angle and yaw sensors tell the stability control where the car is going. When one of them drops off the network, the systems that depend on it switch themselves off and light their warnings. The brakes themselves keep working, but without ABS or stability control, and an electric power steering that loses its module can become heavy.
What causes U0121?
- A blown fuse for the ABS or power steering module, which draw a lot of current
- A corroded connector at the ABS unit, which sits low in the engine bay
- A failed sensor module, such as a yaw rate or steering angle sensor
- Damaged wiring after work on the suspension, the steering or the wheel arches
- A failed ABS module
What to check first for U0121
- Note which warning lights are on: ABS, stability control, tire pressure or steering
- Check the fuses for the module the code names, often a large one for the ABS pump
- Inspect the ABS unit's connector for corrosion and a loose latch
- Ask whether the steering angle sensor needs calibrating after recent alignment or steering work
Can you drive with U0121?
Drive gently and only to a workshop, leaving more distance to brake, since ABS and stability control may be off. If the steering becomes heavy, the park brake will not release or the brake warning light is on, have the car towed.
Since May 2018 an engine warning light that stays on is a major defect at the MOT, so the car fails until the fault is fixed.
Codes on this page
12
- U0121Lost Communication With Anti-Lock Brake System (ABS) Control Module
- U0122Lost Communication With Vehicle Dynamics Control Module
- U0123Lost Communication With Yaw Rate Sensor Module
- U0124Lost Communication With Lateral Acceleration Sensor Module
- U0125Lost Communication With Multi-axis Acceleration Sensor Module
- U0126Lost Communication With Steering Angle Sensor Module
- U0127Lost Communication With Tire Pressure Monitor Module
- U0128Lost Communication With Park Brake Control Module
- U0129Lost Communication With Brake System Control Module
- U0130Lost Communication With Steering Effort Control Module
- U0131Lost Communication With Power Steering Control Module
- U0132Lost Communication With Ride Level Control Module
Related codes
Checked on · Rafael Soares
These are the generic meanings every manufacturer shares. Each brand adds its own detail, so your car's handbook, its service information and a qualified mechanic have the last word. OdoKeep has no connection with any manufacturer, and the app does not read codes from the car.
