Transmission Speed Sensor: Description and Operation

Transmission Speed Sensor

The transmission speed sensor measures the transmission input speed.

The slip of the clutch is determined by comparison of the engine speed with the transmission input speed in the SMG control module. The speed signals enable the SMG control module to detect the slip point of the clutch. This means that for every engine start-up a calibration of the slip point is carried out to prevent the engine from stalling.

Brief description of components
The transmission speed sensor is an inductive sensor and it is located at the front right of the transmission case (clutch housing) at the same height as the layshaft.

The transmission speed is calculated from the impulse sequence.

The signal can only be checked if the vehicle is moving.

Possible faults
Alongside cable and plug-in contact faults, the following faults are conceivable:
- Sensor defective
- Air gap between sensor and sender shaft too large (sensor loose?)
- Sender shaft defective or soiled