Coolant Temperature Sensor/Switch (For Computer): Description and Operation

ENGINE COOLANT TEMPERATURE SENSOR (ECT SENSOR)
The engine coolant temperature sensor, located in the engine coolant passage of the cylinder head. It detects the engine coolant temperature and relays signals to the ECM. It employs a thermistor which is sensitive to changes in temperature. The electric resistance of a thermistor decreases in response to temperature rise. The ECM judges engine coolant temperature by the sensor output voltage and provides optimum fuel enrichment when the engine is cold.