Sensor nach dem Tausch nicht angelernt

A sensor was fitted correctly and never taught what its readings mean.

A great many sensors report a raw position, angle or count that is meaningless until it is anchored to a reference. A steering angle sensor reports a number; which number means straight ahead is a stored calibration. A ride height sensor reports a lever position; what that position is in millimetres is stored. A radar reports a bearing to an object; where straight ahead lies is stored. An occupant classification system reports a load; the empty-seat value is stored.

So a new sensor arrives correct and uncalibrated, which is not the same as working. It reports confidently, consistently and wrongly, and every downstream system believes it — because from inside the vehicle a stable plausible signal is indistinguishable from a true one.

That is why the failure is easy to miss and expensive to leave. Nothing rattles, nothing is intermittent, and the fault is a system quietly acting on a wrong reference.

Two things widen this beyond sensor replacement itself.

Ordinary mechanical work requires the same calibrations. A four-wheel alignment, a steering rack, track rod ends, suspension components, a windscreen carrying a camera, a bumper carrying a radar — all of them move a reference without touching a sensor, and all of them need the calibration redone afterwards. A fault appearing immediately after that kind of work is very often a step nobody performed rather than anything broken.

And reprogramming a module can clear its stored calibrations, so the procedure belongs at the end of a software repair as well. Until it is done the warning lamp stays on and the system stays off, which looks exactly like a repair that failed and is a few minutes' work.