Engine Coolant Temperature Sensor

Engine Coolant Temperature Sensor

The engine coolant temperature sensor is used to sense engine coolant temperature. The sensor protrudes into an engine water jacket.

The ECT sensor is a negative temperature coefficient thermistor (resistance varies inversely with temperature). This means at cold temperatures its resistance is high so the voltage signal will be high. As coolant temperature increases, resistance decreases and the signal voltage will be low. This allows the sensor to provide an analog voltage signal to the engine control module.