Vehicle Speed Sensor: Description and Operation

The vehicle speed sensor generates a signal which indicates the vehicle speed and provides a pulse signal to the ECM, TCM and the modules calculate the vehicle speed. The speedometer cable rotates a magnetic which closes the contacts of a reed switch as it rotates. The reed switch contacts close and open four time for each revolution of the speedometer cable.

The number of pulses per minute increases/decreases with the speed of the car.