The Transmission Fluid Temperature (TFT) sensor sends a signal to the Powertrain Control Module (PCM), which uses it to define shift points, line pressure, as well as control of the Torque Converting Clutch (TCC). Usually, this sensor is placed in the transmission oil pan.
The TFT sensor has 5 volts of reference provided by the PCM. The internal resistance of the sensor changes according to the temperature of the transmission fluid and sends a return signal to the PCM. In other words, TFT sensors are defined as a negative temperature coefficient thermistor. It means that the internal resistance is inversely proportional to the oil temperature. The voltage of the TFT sensor signal decreases as the transmission fluid temperature increases, if the temperature decreases, the voltage increases.
The DTC code P0713 OBDII is stored when the PCM finds a high signal in the TFT Sensor due to an open circuit.