Note. For circuit reference, see WIRING DIAGRAMS article.
Circuit Description
Engine Coolant Temperature (ECT) sensor is a variable resistor, sometimes called a thermistor, that measures temperature of engine coolant. The PCM supplies 5 volts to ECT signal circuit. When ECT is cold, sensor resistance is high. When ECT increases, sensor resistance drops. With high sensor resistance, PCM detects a high voltage on ECT signal circuit. With lower sensor resistance, PCM detects a lower voltage on ECT signal circuit. If PCM detects an excessively high ECT signal voltage, which is a low temperature indication, this DTC will set.