Vehicle Speed Sensor (VSS)

Vehicle speed sensor generates a pulsed vehicle speed signal to the ECU. Speed sensor consists of a reed switch and rotating permanent magnet, which are installed in speedometer unit. Changes in polarity caused by the rotating magnet (located adjacent to the reed switch) open and close reed switch, which has a constant polarity of its own.

A second speed sensor consisting of a Permanent Magnet (PM) generator and pick-up coil assembly is located in the transmission. Rotating PM generator produces an AC voltage signal in the winding of the pick-up coil. Signal generated by speed sensor is utilized by transmission control unit and monitored by ECU.