Automatic Transmission Fluid Temperature Sensor Assembly

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.

Fig 1: Automatic Transmission Fluid Temperature Sensor Assembly

Courtesy of GENERAL MOTORS CORP.

The automatic transmission fluid temperature (TFT) sensor assembly is a thermistor which is mounted in the wiring harness assembly. Low transmission temperature produces high resistance, while high temperature produces low resistance. The PCM supplies a 5-volt signal to the TFT sensor assembly through an internal resistor. Then the PCM measures the voltage drop in the circuit. Voltage is high when the transmission is cold and low when the transmission is hot.

The PCM uses the TFT sensor assembly in order to regulate torque converter clutch apply, as well as shift quality.

DTCs P0711, P0712 and P0713 indicate a fault in the TFT Sensor Assembly circuit. After the vehicle has been started, transmission temperature should rise steadily and stabilize between 90-115°C (194-239°F), depending on load. All three DTCs causes the PCM to use a default value of 140°C (284°F), thus reacting as if the transmission were hot in either case. When DTCs P0711, P0712 or P0713 are set, the PCM freezes the shift adapts from being updated, and the MIL illuminates. Some driveability symptoms will be noticed, especially when cold.