The Intake Air Temperature Sensor (IATS) is installed into the Barometric Pressure Sensor (BPS). The IATS uses a thermistor whose resistance changes with the temperature. The electrical resistance of the IATS decreases as the temperature increases, and increases as the temperature decreases. The 5V power source in the PCM is supplied to the IATS via a resistor in the PCM. That is, the resistor in the PCM and the thermistor in the IATS are connected in series. When the resistance value of the thermistor in IATS changes according to the intake air temperature, the signal voltage also changes. The PCM uses the IAT signal to correct basic ignition timing and fuel injection duration.