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 fluid temperature (TFT) sensor is a two wire sensor, consisting of a TFT sensor signal circuit and a low reference circuit, supplied by the transmission control module (TCM). The TFT sensor continuously monitors the temperature of the transmission fluid in the transmission sump. When the transmission fluid is cold the TFT sensor resistance is high, resulting in high voltage on the signal circuit. As the transmission fluid temperature increases, the TFT sensor resistance decreases, resulting in a lower voltage on the signal circuit. The TCM determines the transmission fluid temperature based on the voltage.