Vehicle Speed Sensor
WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The Vehicle Speed Sensor (VSS) assembly provides vehicle speed information to ECM. The VSS assembly is a Permanent Magnet (PM) generator. The PM generator produces a pulsing AC voltage as rotor teeth on the transmission output shaft pass through the sensor's magnetic field. The AC voltage level and the number of pulses increase as speed of the vehicle increases. Output voltage varies with speed from a minimum of 0.5 volt at 100 RPM to more than 100 volts at 8000 RPM. The ECM converts the pulsing voltage to vehicle speed. The ECM uses the vehicle speed signal to determine shift timing and TCC scheduling.