Engine Coolant Temperature Sensor

Engine Coolant Temperature (ECT) sensor is a thermistor device in which resistance changes with temperature. Electrical resistance of a thermistor decreases as temperature increases, and increases as temperature decreases. Varying resistance affects voltage drop across sensor terminals and provides electrical signals to PCM corresponding to temperature. Thermistor type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying resistance of passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor in a series with sensor resistor determines voltage signal at PCM. This voltage signal is equal to reference voltage minus voltage drop across fixed resistor. ECT measures temperature of engine coolant and is threaded into an engine coolant passage. ECT sensor is similar in construction to IAT sensor.