Fuel Temperature Sensor is NTC thermistor which voltage gets low if the temperature comes to be high. It is installed in fuel supplying line. It senses the temperature of fuel supplied to high pressure pump. Fuel temperature is limited (engine power is limited) to keep fuel temperature from reaching at 80℃(176℉). This limit is to protect fuel line such as high pressure pump and injectors from damages due to rapid deterioration by vapor-lock phenomenon which can occur at high temperature or destruction of oil membrane.