Capteur de régime de turbine défectueux

The sensor reading the torque converter's turbine — the transmission's input speed — failed or reading erratically. It is one half of every ratio calculation the gearbox makes: input divided by output gives the ratio actually being achieved, and each gear has exactly one correct answer.

Which means a fault here does something unusual — it silences monitors rather than triggering them. Gear ratio checks, slip detection and torque converter lock-up monitoring all depend on this signal, so a car with a turbine speed fault often shows fewer transmission codes than it should. A slipping element can hide behind it, which is why a re-scan after the repair is worth asking for.

What the driver notices is lock-up. Without input speed the module cannot manage the torque converter clutch smoothly, so it is usually disabled — which shows as higher revs at a steady cruise, worse economy, or a shudder.

Two location-specific causes dominate. Transmission fluid wicks along the wires into the connector and bridges the terminals, and swarf collects on what is a magnetic sensor inside a gearbox. A heavily bearded sensor is reporting on the gearbox rather than on itself.

Ask where it is fitted before agreeing a price — external on some transmissions, behind the sump or valve body on others, for the same code.