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 has 2 pressure control solenoids that controls the flow of transmission fluid to engage clutches. The flow is directed through shift valves that allows it to engage different clutches. The vehicle speed sensor and automatic transmission turbine speed sensor contains a permanent magnet surrounded by a coil that gives off a continuous magnetic field. As the vehicle is driven, a speed sensor rotor located near the magnetic pickup of the speed sensor coil also rotates. This rotation produces a variable AC voltage signal. The frequencies of the signals are proportional to the transmission turbine and output speeds. The transmission control module (TCM) uses the signals to calculate the gear ratio. The TCM compares the computed ratio to the commanded gear ratio.