Circuit Description

Engine Coolant Temperature (ECT) sensor contains a thermistor which changes resistance based on temperature. ECT sensor is located in coolant crossover pipe at center rear of engine. Sensor has a signal and ground circuit. ECM applies about 5 volts on signal circuit of sensor. ECM monitors changes in voltage caused by changes in resistance of sensor to determine engine coolant temperature.

When engine coolant is cold, sensor resistance is high. ECM will sense a high signal voltage (low temperature). When engine coolant is warm, sensor resistance is low. ECM will sense a low signal voltage (high temperature). When the difference between calculated engine coolant temperature and actual engine coolant temperature is greater than 7°F (12°C), DTC will set. For duplication of DTC, ensure engine is running.