Test the TEMPERATURE SENSOR with cigarette lighter and multimeter

The car engine temperature sensor is an NTC resistor encapsulated in a brass tube and with two terminals on a plastic edge.
Sometimes there can be three terminals in the connector, but only two are used as in the two-terminal sensor, the third terminal can be used for grounding.
An NTC resistor drops its resistance when it gets hot, that's why you can use a lighter to heat the tip of the engine temperature sensor for about 45 seconds until the resistance drops completely, after that the tip of the sensor will start to cool making the resistance of the sensor rise little by little, until reaching the resistance of room temperature.