Vehicle Speed Sensor: Description and Operation

Vehicle Speed Sensor (VSS)
The PCM determines the speed of the vehicle by converting a pulsing voltage signal from the vehicle speed sensor (VSS) into miles per hour. The PCM uses this signal to operate the cruise control, speedometer, and the TCC and shift solenoids in the transmission. For more information on the TCC and shift solenoids, refer to Automatic Transmission.


With the starter switch in ON or START, the VSS receives power. For every rotation, the VSS outputs four pulses to the engine (M/T) or powertrain (A/T) control module (ECM or PCM), and the speedometer to gauge speed.