Capteur de pression de direction assistée défectueux

The sensor reporting hydraulic pressure in a conventional power steering system — and its purpose is not steering at all, which is what makes it worth understanding.

Its job is to warn the engine. Turning the wheel at parking speed loads the steering pump heavily, and that load is enough to pull an idling engine down and stall it. The sensor tells the engine module that a large load is arriving so it can raise idle speed to meet it.

So the characteristic symptom is an engine problem rather than a steering one: a stall or a dip in idle when the wheel is turned at low speed, particularly with the air conditioning also running. A car that stalls while parking is very often this, and it is looked for in the idle control system rather than the steering.

The sensor sits in the high-pressure line, so leaks at its fitting are as common as electrical failure, and a weeping sensor is often found by the fluid loss rather than the code.

One check comes first and is free: the fluid level and condition. Low or aerated fluid produces erratic pressure the sensor honestly reports, and the same low level makes the pump whine and the steering heavy at low speed. Dark, burnt-smelling fluid is a system that has been running hot, which points at a restriction rather than at the sensor.