Theory Of Operation

The purpose of the diagnostic is to check the transmission sump oil temperature sensor for electrical failures by continuously monitoring the sensor output circuit for voltage high, low, or open conditions. This fluid sensor (thermistor), which correlates resistance to temperature, measures the temperature of the fluid in the sump (oil pan). Temperature values are calculated by the TCM based on the sensor's voltage output for shift map determination, torque converter fluid temperature rationality checks, etc. If the measured temperature sensor output circuit voltage is greater than or equal to a calibrated high threshold (circuit high or open) or is less than or equal to a calibrated low threshold (circuit low) for a calibrated amount of time, a fault code will be set.