Vehicle Speed Sensor: Description and Operation

Vehicle Speed Sensor (VSS)
The VSS is part of the speedometer and is located in the instrument panel assembly. The VSS consists of a reed switch and a magnet. The magnet turns with the speedometer cable, causing the reed switch to turn ON and OFF. The ON and OFF frequency of the reed switch increases or decreases in proportion with the vehicle speed. The powertrain control module (PCM) receives a digital signal from the VSS.