Circuit Operation

The vehicle speed sensor generates a signal that is proportional to vehicle speed. The signal produced is a sine wave, which the Powertrain Control Module (PCM) processes into a square wave. The PCM provides the speed signal to speedometer, Magna Steer Module, and for Buick only, the Multi-Function Chime Module.

The PCM takes the voltage pulses from the vehicle speed sensor on YEL (400) and PPL (401), and uses them to close a solid-state output switch. The output terminal DK GRN/WHT (817) is switched to ground at a rate that is proportional to vehicle speed.