Módulo de control de la dirección asistida averiado

The controller driving an electric power steering motor.

It should be near the bottom of any list, because almost everything that looks like it is something else — and the something elses are far cheaper. Calibration is the first: the steering angle sensor learns where straight-ahead is, and a vehicle that has had an alignment, a rack, a clockspring or suspension work without being re-zeroed reports a confidently wrong angle on perfect hardware. Road speed is the second: assistance is chosen by speed, so an implausible wheel speed from a failing sensor upsets the steering as a knock-on. And supply is the third — electric steering draws a large current under load, so a poor connection or a tired battery makes it derate.

When the module genuinely has failed, the symptom is usually consistent rather than intermittent: assistance gone or fixed at one level from every start, not varying with conditions.

The reassurance that belongs on every one of these: the steering does not fail. The mechanical connection between wheel and road remains, so the car steers — it just becomes much heavier, most noticeably when parking. What is worth warning a driver about is that the change can happen while moving, possibly mid-corner, so knowing in advance matters.

On many vehicles the module is integrated into the steering rack or the column motor and is not supplied separately, which makes establishing that it really is the fault worth doing properly.