Theory Of Operation

The purpose of the diagnostic is to detect circuit failures on the Transmission Oil Temperature Sensor circuits. The Transmission Oil Temperature Sensor is located in the sump of the transmission and can be monitored with a scan tool under the Oil Temperature Sensor data parameter. This sensor is a 2-wire thermistor with a Negative Temperature Coefficient (NTC). This means that as the temperature increases, the resistance of the sensor decreases. A Sensor Ground circuit and a 5-volt signal circuit are provided by the Transmission Control Module (TCM).

If the TCM detects a signal voltage above or below a calibrated threshold, a DTC that is relevant to the failure will set.

The Transmission Oil Temperature Sensor is integral with the Transmission Internal Wire Harness. If it is necessary to replace the sensor, the entire Internal Wire Harness must be replaced.

The following table shows the relationship between temperature and resistance of the Transmission Oil Temperature Sensor.