What does U0126 mean?

U0126 means the network stopped hearing from the steering angle sensor module, which lives in the steering column area, usually behind or near the clockspring. That sensor tells the stability control system where the front wheels are pointed, so when it goes quiet the vehicle disables the functions that depend on it: stability control and traction control commonly drop out, lane-keeping and driver-assist features may switch off, and some vehicles post a steering or power-steering warning as well. Basic steering is mechanical and still works, so the car remains controllable — but it no longer has the electronic help that keeps it pointed straight on a slippery surface. The most useful thing to know about this code is that it frequently follows service work. A battery disconnect, a jump start, a dead battery, an airbag or clockspring repair, or an alignment can leave the steering angle sensor out of calibration, and many vehicles need a steering-angle relearn before the system will come back. That is why the diagnostic order starts with voltage and calibration rather than parts. Test the battery and charging system, scan every module to see whether this is one fault or a shared bus problem, then check whether a steering-angle recalibration is required — a capable scan tool performs it in minutes. If the code stays, move to the hardware around the sensor: inspect the connector at the sensor and the clockspring for backed-out pins and corrosion, and trace the wiring up the column, where repeated steering movement and past column work are common sources of broken conductors. Replacing the sensor or clockspring is the last step, not the first, and a new sensor still needs calibration afterwards, so a replacement without a relearn simply leaves the light on. Until it is fixed, drive gently, especially in rain or snow, and avoid relying on driver-assist features that may be disabled.