Engine Coolant Temperature (ECT) Sensor
The ECT sensor is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.
If the PCM receives a high engine temperature signal from the ECT, it adjusts fueling rates to protect the engine from damage due to overheating.