Vehicle Speed Sensor: Description and Operation

Vehicle Speed Sensor:

PURPOSE
The Vehicle Speed Sensor (VSS) is a pulse counter type input that informs the Powertrain Control Module (PCM) how fast the vehicle is being driven. The VSS system uses an inductive sensor mounted in the tail housing of the transmission and a toothed reluctor wheel on the tail shaft. As the reluctor rotates, the teeth alternately interfere with the magnetic field of the sensor creating an induced voltage pulse.

OPERATION
The VSS produces an AC voltage signal that increases with vehicle speed. The PCM processes this signal and sends it to the instrument panel, radio, Central Control Module (CCM), chime module and cruise control module on CKT 817.

DIAGNOSTIC NOTES
A speed sensor or circuit which is not functioning properly will set a Diagnostic Trouble Code (DTC) 24 or 72.