Transmission Fluid Temperature Sensor

The temperature sensor is a negative temperature coefficient thermistor (temperature sensitive resistor) that provides information to the Powertrain Control Moduel (PCM) regarding the transmission fluid temperature. The temperature sensor clips on to the valve body, and is replaced as a part of the A/T wiring harness. The sensor monitors pressurized main line pressure from the inside of the valve body in order to determine the operating temperature of the transmission fluid.

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 temperature sensor and the PCM measures the 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 measures this voltage as another input in order to help control line pressure, shift schedules, and Torque Converter Clutch (TCC) apply. when the transmission fluid temperature reaches 130° C (266° F), the PCM enters hot mode. Above this temperature the PCM modifies the transmission shift schedules and the TCC apply in an attempt to reduce the fluid temperature by reducing the transmission heat generation. During hot mode the PCM applies the TCC at all times in Third and Fourth gears. Also, the PCM performs the 2-3 and the 3-4 shifts earlier in order to help reduce fluid heat generation.

The PCM stays in hot mode until the temperature drops below 120° C (248° F).