With Powertrain Control Module (PCM)

Vehicle Speed Sensor (VSS):

The Vehicle Speed Sensor (VSS) is made up of a coil mounted on the transmission and a tooth rotor mounted to the output shaft in the transmission. As each rotor tooth nears the coil, the coil produces an AC voltage pulse. As the vehicle speed increases, the number of AC voltage pulses per second increases. On Powertrain Control Module (PCM) equipped vehicles the vehicle speed signal buffer processes inputs from the VSS and output signal to the speedometer control module, and cruise control module.

The VSS buffer signal takes the voltage pulses from the VSS and uses them to open and close four solid state output switches to ground at a rate proportional to vehicle speed. The VSS buffer is matched to the vehicle based on final drive ratio and tire size. It is important to ensure that the correct VSS buffer is installed in the vehicle if replacement is necessary.