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 to supply inputs to the speedometer, the multi-function chime (MFC) module, computer command ride (CCR) module (if equipped), and heads-up display module (if equipped).

The PCM takes the voltage pulses from the vehicle speed sensor, through the PPL and YEL wires, and uses them to close a solid-state output switch. The output terminal is switched to ground at a rate that is proportional to vehicle speed.