Note. For circuit reference, see WIRING DIAGRAMS article.
Circuit Description
Engine Coolant Temperature (ECT) sensor is a thermistor 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 less than 1.5 volt.
Conditions for setting DTC are: engine running, ECT sensor signal is intermittently greater than 283°F (140°C) and conditions present for greater than 15 seconds.