Vehicle Speed Sensor (VSS)

The VSS is threaded in the back of the transaxle case near the differential housing. The VSS produces an AC voltage of different amplitude and frequency depending on the velocity of the output shaft. The VSS produces the signal from 16 evenly spaced notches on the transaxle differential carrier. The VSS produces a readable AC voltage signal when vehicle speed is above 5 km/h (3 mph). The VSS signal is sent to the PCM, which is used to determine the RPM of the output shaft.

ODOMETER - The VSS produces 5000 readable pulses/mile between 5 and 161 km/h (3-120 mph), which are sent to the PCM to determine vehicle speed. The vehicle speed input is used to determine the miles the vehicle has traveled. The PCM reads the VSS signal and sends vehicle speed information to the BCM over the Class II link. The BCM in turn calculates the distance traveled and sends the information to the I/P cluster over the link. The I/P cluster increments the electronic odometer accordingly.

SPEEDOMETER - The VSS voltage pulses are sent to the PCM to determine vehicle speed. The PCM averages the vehicle speed calculations over time then sends it to the I/P cluster over the Class II link every 100 ms.

Averaging the information allows the speedometer to obtain smooth speedometer needle fluctuations.

The VSS signal is also used for many engine emission control calculations, idle speed adjustment and transaxle shift points.