Vehicle Speed Sensor: Description and Operation

Vehicle Speed Sensor (VSS):

The Vehicle Speed Sensor (VSS) is a gear driven permanent Magnet generator housed in the vehicle's transaxle. This sensor generates a sine wave output with a frequency proportional to vehicle speed. The ECM converts this signal to an output that is switched to ground at a frequency of 4000 pulses per mile. This output is pulled up to 5 volts or greater by the components that use this speed signal as an input.

The VSS provides information to the ECM for control of idle speed and transmission converter clutch engagement as well as controlling canister purge of the fuel evaporative emission system.