Vehicle Speed Sensor: Description and Operation

Vehicle Speed Sensor:

PURPOSE AND OPERATION
The Vehicle Speed Sensor (VSS) provides road speed data to the Engine Control Module (ECM). The ECM in turn detects vehicle movement from the road speed input and ensures that idle air control mode is disengaged. Should the vehicle speed sensor fail in service, the ECM idle air control would become erratic.

The sensor also provides road speed data to the electric speedometer and cruise control ECM.