The coolant temperature sensor consists of a negative temperature coefficient thermistor that is very sensitive to temperature changes. When the engine coolant temperature gradually increased, Thermistor resistance will gradually decline. On the contrary increases, When the engine coolant temperature changes, The output voltage of the sensor also changes accordingly.

Engine coolant temperature sensor elongated head contact with the cooling liquid, The temperature of the coolant is detected by the change of the resistance value. And this signal is sent to the ECU,Used to detect the engine coolant temperature. The ECU corrects the fuel injection time and the ignition time after receiving the temperature signal.
The normal use of the coolant temperature sensor is -30 ° C to 120 ° C, The corresponding output voltage is 0.3V ~ 4.7V. When the ECU detects an output voltage signal beyond this range, You can determine the sensor circuit failure.