Vehicle Speed Sensor: Description and Operation

Vehicle Speed Sensor (VSS):

This sensor is located in the extension housing of the transaxle, and it generates 8 voltage pulses (sent directly to the engine controller) for every revolution of the axle shaft. The engine controller uses these signals along with the signals from the Throttle Position Sensor (TPS) to determine a closed throttle deceleration condition or a closed throttle idle (vehicle stopped) condition.

Under idle (vehicle stopped) conditions, the engine controller sees that there are no signals being generated from the vehicle distance (speed) sensor, and it adjusts the Automatic Idle Speed (AIS) motor to maintain a desired engine idle speed. Under closed throttle deceleration, the engine controller receives signals from the vehicle distance (speed) sensor, because the vehicle is still moving, and it adjusts the AIS motor to maintain a desired Manifold Absolute Pressure (MAP) value.