Note. For circuit reference, see WIRING DIAGRAMS - 4.3L article.
Circuit Description
Engine Coolant Temperature (ECT) sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. Low temperature will result in a high signal voltage. DTC will set when VCM sees an ECT sensor voltage of greater than 5 volts and engine run time is greater than 5 seconds.