Engine Coolant Temperature Sensor

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The Engine Coolant Temperature (ECT) sensor is a variable resistor, that measures the temperature of engine coolant. ECT sensor is located on side of left cylinder head. See Figure. The PCM supplies 5 volts to the ECT sensor signal circuit and ground for the ECT sensor low reference circuit. When ECT is cold, sensor resistance is high. When ECT increases, sensor resistance decreases. With high sensor resistance, PCM detects a high voltage on ECT sensor signal circuit. With lower sensor resistance, PCM detects a lower voltage on the ECT sensor signal circuit. If PCM detects an out-of-range signal voltage, a DTC will set. To diagnose, perform related diagnostic test. See DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - 4.8L, 5.3L & 6.0L "C", "K" & "N" SERIES - FLEX FUEL & GASOLINE article.