Transmission Fluid Temperature Sensor
The Transmission Fluid Temperature (TFT) sensor is a negative temperature coefficient thermistor that provides information to the PCM regarding transmission fluid temperature. The TFT sensor is integrated in the TFP manual valve position switch assembly which is bolted to the control valve body. The sensor monitors main line pressure from the inside of the control valve body to determine the operating temperature of the transmission 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 transmission fluid. The PCM sends a 5-volt reference signal to the sensor. This measures the voltage drop in the electrical circuit. A lower fluid temperature creates a higher resistance in the TFT sensor, thereby measuring a higher voltage signal.
The PCM measures this voltage as another input to help control line pressure, shift schedules and TCC apply. When the transmission fluid temperature reaches 284°F (140°C), the PCM enters hot mode. Above this temperature, the PCM modifies the 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 applies TCC at all times in 3rd and 4th gears. Also, the PCM performs the 2-3 and the 3-4 shifts earlier to help reduce the generation of fluid heat. (Схема №46)