Circuit Description: Notes

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the ECT signal circuit and supplies a ground to the low reference circuit. The PCM monitors the mutual performance of the ECT and the intake air temperature (IAT) signals. The PCM monitors the warm up and cool down behavior of the sensors, after a vehicle driven at operating temperature is shut down. If the PCM detects that the ECT is not with in a predetermined range of IAT after a long soak, or the ECT and IAT are not within a range of each other, as compared to a previous cold start, this DTC sets.

The following table illustrates the difference between temperature, resistance, and voltage: