Vehicle Speed Sensor: Description and Operation

PURPOSE
The vehicle speed sensor reports road speed to the ECM. This information is used to synchronize emission systems and to adjust for various engine demands.

LOCATION
The sensor is mounted in the back of the speedometer cluster.

CONSTRUCTION
The sensor is a reed switch that is controlled by a rotating magnet inside to transaxle. As the magnet passes under the sensor the contacts close momentarily, resulting in a ground at the ECM. Four pulses are produce for each sensor revolution.