Circuit Description

WARNING: This page is about a different car, the 2005 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.

The automatic transmission fluid temperature (TFT) sensor is part of the automatic transmission internal wiring harness assembly. The TFT sensor is a thermistor, or a resistor that changes value when the temperature changes. The sensor has a negative-temperature coefficient. This means that as the temperature increases, the resistance decreases, and as the temperature decreases, the resistance increases. The transmission control module (TCM) supplies a 5 volt reference signal to the sensor and measures the voltage drop in the circuit. When the transmission fluid is cold, the sensor resistance is high and the TCM detects high signal voltage. As the fluid temperature increases, the resistance of the sensor decreases, which lowers the signal voltage.

If the TCM detects an open in the TFT sensor or signal circuit, then DTC P0713 sets. DTC P0713 is a type C DTC.