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. Switching action frequency is interpreted by the ECU as vehicle road speed and used in calculations for these outputs:

Fuel injection quantity
Idle speed control
Ignition timing control