The vehicle's controller area network (CAN) or specialized serial data bus relies on periodic heartbeat and data message transmissions from the steering angle sensor or integrated steering column module. Receiving control modules (such as the ABS, ESC, or BCM) monitor message reception intervals; U0126 indicates that expected communication from the steering-angle sensor/module or integrated steering-angle function became unavailable or was not received according to the vehicle's network-supervision strategy. Note that malformed or invalid-data faults may belong to different DTC families and should not automatically be treated as the same condition as lost communication.