Vehicle Speed Sensor: Description and Operation

PURPOSE
The Vehicle Speed Sensor (VSS), sends a pulsing voltage signal to the Engine Control Module (ECM), which the ECM converts to miles per hour. This Sensor helps to control the operation of the Idle Air Control System. The number of pulses generated is four pulses per one rotation of the Pinion Shaft.

OPERATION
- The Vehicle Speed Sensor generates a signal which indicates the Vehicle speed to the Speedometer. The Speedometer consists of a Vehicle Speed Sensor, an ammeter (needle movement), stepper motor (odometer), and a driving circuit (printed circuit board).
- The Vehicle Speed Sensor is mounted to the Transmission. The Transmission Pinion Shaft rotates and generates four pulses per one rotation. The rate at which the pulses are generated indicates the Vehicle speed. The Vehicle Speed Sensor (in the Speedometer) uses the pulses to control needle movement, and sends vehicle speed information to the Engine Control Module (ECM) and the Cruise Control Unit. The Speedometer sends 4096 pulses per mile; the frequency of these pulses indicates the Vehicle speed.