Transaxle Fluid Temperature (TFT) Sensor

The Transaxle Fluid Temperature (TFT) sensor is a negative temperature coefficient thermistor that provides information to the PCM/TCM regarding transaxle fluid temperature. The temperature sensor is integrated in transaxle fluid pressure switch assembly which is bolted to the control valve body. The sensor monitors main line pressure from the inside of the control valve body in order to determine the operating temperature of the transaxle fluid. The sensor uses an O-ring seal to maintain fluid pressure in the control valve body.
The internal electrical resistance of the sensor varies in relation to the operating temperature of the transaxle fluid. The PCM/TCM sends a 5-volt reference signal to the temperature sensor, then measures voltage drop in the electrical circuit. A lower fluid temperature creates a higher resistance in the temperature sensor, thereby measuring a higher voltage signal.
The PCM/TCM measures this voltage as another input to help control line pressure, shift schedules and TCC apply. When the TFT reaches 140°C (284°F), the PCM/TCM enters hot mode. Above this temperature the PCM/TCM modifies the transaxle shift schedules and TCC apply in an attempt to reduce fluid temperature by reducing the amount of heat generated by the transaxle. During hot mode the PCM/TCM applies TCC at all times in Third and Fourth gears. Also, the PCM/TCM performs the 2-3 and 3-4 shifts earlier in order to help reduce heat generated in transaxle fluid.