Vehicle Speed Sensor: Description and Operation

Vehicle Speed Sensor:

The vehicle speed sensor, located in the speedometer head assembly, consists of a contact set and magnet that turns with the speedometer cable. Magnet movement causes the contacts to alternately open and close four times per cable revolution. The frequency of the on-off signal from the sensor is used to calculate the vehicle road speed, and influences the following outputs:

Fuel injection quantity
Idle speed control
Ignition timing control