When it is predicted that an engine is going to be started in the near future, a heater portion of an air flow meter is energized so as to be heated in advance. Prior to the pre-heating, an intake air temperature is sensed by a temperature sensing portion of the air flow meter. After completion of start-up of an intake air temperature sensor, a difference between the intake air temperature sensed by the intake air temperature sensor and the previously sensed intake air temperature is obtained. When the difference is above a predetermined value, it is judged that the intake air temperature sensor or the air flow meter is in an abnormal condition.