Installed in the fuel supplying line, the Fuel Temperature Sensor (FTS) senses the temperature of fuel supplied to the high pressure pump. The thermistor of FTS has a characteristic of Negative Temperature Coefficient (NTC), which means temperature and resistance are inversely propoertional to each other. ECM uses the sensor signals to control the fuel amount, and controls the engine output by limiting fuel injection in order to prevent excessive rise of temperature. This can prevent vapor-lock at high temperature or destruction of oil membrane, which can deteriorate lubricating performance of fuel, causing damage to high pressure fuel pump and injector.