Engine - Coolant Temperature Sensor/Switch: Description and Operation

ENGINE COOLANT TEMPERATURE (ECT) SENSOR
The engine coolant temperature sensor is installed in the engine coolant passage of the cylinder head, detects engine coolant temperature and emits signals to the ECM. This part 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.