Nubira CDX Wagon L4-2.0L DOHC D-TEC MFI (2000)
Transmission Temperature Sensor/Switch: Description and Operation
TRANSMISSION FLUID TEMPERATURE (TFT) SENSOR
The TFT sensor is a negative temperature coefficient thermistor (temperature sensitive resistor) that provides information to the PCM regarding
transmission fluid temperature. The temperature sensor is integrated in the TR switch val. position sw. which is volted to the valve body. The sensor
monitors pressurized main line pressure from the inside of the valve body to determine the operating temperature of the transaxle fluid. The sensor,
similar to each of the TR switch val. position sw., uses an O-ring seal to maintain fluid pressure in the valve body.
The internal electrical resistance of the sensor varies in relation to the operating temperature of the transmission fluid (see chart).
The PCM sends a 5 volt reference signal to the temperature sensor and 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 to help control line pressure, shift schedules and TCC apply. When transaxle fluid temperature
reaches 284°F (140°C) the PCM enters "hot mode." Above this temperature the PCM modifies transmission ship schedules and TCC apply in an
attempt to reduce fluid temperature by reducing 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 3-4 shifts earlier to help reduce fluid heat generation. Hot mode may not be available on some
applications.
