Coolant Temperature Sensor/Switch (For Computer): 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 the temperature rise.

The ECM judges engine coolant temperature by the sensor output voltage and provides optimum fuel enrichment when the engine is cold.


The Engine Coolant Temperature (ECT) sensor is located in the coolant passage of the cylinder head.

The ECT sensor is a variable resistor whose resistance changes as the temperature of the engine coolant flowing past the sensor changes. When coolant temperature is low, sensor resistance is high; when coolant temperature is high, sensor resistance is low.

The Engine Control Module (ECM) checks ECT sensor voltage and uses the information to adjust fuel injector pulse width and ignition timing. When the temperature sensed is very cold, the ECM enriches the fuel mixture and advances ignition timing. As coolant temperature rises, the ECM reduces the amount of enrichment and timing advance.