open learning is interrupted in the same way as in the case where the engine speed monitoring unit 280 operates normally and an increase in the engine speed is sensed malfunctioning of engine speed monitor 280 probably occurs due to a short circuit or open circuit of wiring and can be detected by a change in the output level of engine speed monitor 280 the foregoing description has been made by way of examples of the full close and the full open learning operations however it may also be applied to a case in which a throttle return spring is to be checked when the throttle control becomes abnormal throttle valve 115 stops the motor drive as a fail safe procedure a return spring is provided for ensuring the throttle valve to return to a predetermined position a default position at this instant the default position is set not at the full closure position but mostly at a position at which the throttle valve 115 is slightly open this is because of ensuring that even if the motor drive is stopped as the fail safe procedure under abnormality of the throttle control the vehicle may be moved at least to a safety position in order to allow for the throttle valve 115 to be moved to a predetermined position at the time when the motor drive.