Capteur de régime de sortie défectueux

The sensor reading the transmission's output shaft, failed or reading erratically. It is the reference against which several other measurements are checked, which is why its faults surface as codes that appear to be about something else — gear ratio monitoring, speedometer drive on many vehicles, torque converter lock-up, and the correlation checks that compare it against wheel speed and road speed.

Most are magnetic or Hall sensors reading a toothed ring, so the ring matters as much as the sensor. A chipped or corroded tooth produces a dropped count at one point in every revolution — erratic in a way a failed sensor is not, and worth distinguishing because the repair is different and deeper.

Swarf is the cause worth naming. These sensors are magnetic and sit inside the gearbox, so they collect the fine metal debris that any transmission produces. A build-up on the tip degrades the signal gradually. On a gearbox that has had a hard life, a bearded sensor is telling you about the gearbox rather than about itself.

Before condemning it, consider that the reading may be honest: a correlation fault can equally mean the tyres or the final drive are not what the module assumes — which costs nothing to establish and is far commoner than a failed sensor.