Transmission Fluid Temperature 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 Transmission Fluid Temperature (TFT) sensor is a thermistor (temperature sensitive resistor) and is part of the Transmission Fluid Pressure (TFP) manual valve position switch. The ECM supplies and monitors a 5-volt signal to TFT sensor. This monitored 5-volt signal is then modified by resistance of TFT sensor. When transmission fluid temperatures are low, TFT sensor resistance is high and ECM sees a high monitored voltage signal. When transmission fluid temperatures are high, TFT sensor resistance is low and ECM sees a low monitored voltage.
ECM uses TFT sensor input to control Torque Converter Clutch (TCC) application and shift quality. Sensor circuit problem should set a related DTC.