(ECT) Engine Coolant Temperature Sensor

An engine coolant temperature sensor or ECT sensor is a variable resistor that uses resistance to change a 5-volt reference signal from the PCM. The sensor's signal changes according to the engine's coolant temperature. It is a vital component for maintaining an engine's normal operating temperature. Located in the coolant stream, usually on or around the thermostat housing. It senses the engine's coolant temperature.

It modifies a 5-volt voltage signal from the ECM concerning the engine's coolant temperature. They are (NTC) or negative temperature coefficient thermistors. As the coolant's temperature increases, the sensor's resistance decreases. More voltage is dropped across this sensor when it is cold than when it is hot.

The ECM uses this signal to adjust engine cooling fans, fuel injectors, and transmission (TCC) torque converter clutch actuators. The symptoms of a faulty ECT sensor include a rich air-fuel ratio, poor fuel mileage, and an inoperative torque converter clutch.