Vehicle Speed Sensor: Description and Operation

PURPOSE
The vehicle speed sensor is used to monitor actual vehicle speed. Vehicle speed information is used by the ECU for fuel injection, air injection (on equipped vehicles), cruise control and electronic control of automatic transmissions.

LOCATION
Located on the backside of the speedometer cluster.

OPERATION
The sensor is a reed switch that is controlled by a rotating magnet. As the magnet passes under the sensor the contacts close momentarily, resulting in a ground signal. The frequency of these ground signals sent to the ECM is relevant to vehicle speed.
The VSS inputs the ECU through terminal SPD.