Circuit/System Description

WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The transmission output speed sensor is a permanent magnet surrounded by a coil of wire that is mounted to the transmission rear housing in 2WD models and on the transfer case on 4WD models. The vehicle speed sensor is positioned next to the gear that is splined to the transmission output shaft in 2WD models and next to a gear on the transfer case output shaft in 4WD models. As the gear rotates, the tips of the gear teeth cross the magnetic field which generates an AC current. The voltage output and frequency generated by the sensor will vary as the speed of the gear changes. The vehicle speed sensor signal wires are twisted to cancel magnetically induced fields. The transmission control module (TCM) changes the speed sensor analog signal into a digital signal.