Circuit Operation

Vehicle speed information is provided to the PCM by the Vehicle Speed Sensor (VSS). The VSS consists of a magnetic pickup sensor mounted to the transmission case which interfaces with a rotor pressed onto to the transmission output shaft.

The VSS produces a frequency signal that is proportional to vehicle speed. The PCM converts the VSS signal to vehicle speed, displayed on the scan tool in miles per hour and kilometers per hour. The PCM also uses the VSS signal to generate the 4000 pulses per mile vehicle speed signal used by the instrument cluster and the stepper motor cruise control module.