Note. For circuit reference, see WIRING DIAGRAMS article.
Circuit Description
Engine Coolant Temperature (ECT) sensor is a thermistor or a variable resistor, that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM sees an ECT sensor voltage intermittently greater than 2 volts.
DTC will set when engine is running, ECT sensor signal voltage is intermittently less than -37°F (-39°C) and condition is present for greater than 3 seconds.