PURPOSE: To judge a failure of opening and closing control of a throttle valve without using a throttle opening sensor for detecting the opening of the throttle valve to reduce cost, and adopt on a vehicle engine on which a mount area for the throttle opening sensor is restricted.
CONSTITUTION: A failure of rotation of a throttle valve 1 due to seizure of a stepping motor 4 and a failure of opening and closing control of the throttle valve 1 produced if the throttle valve 1 is caught by some reason are judged based on a target rotational speed D determined by the depressed amount 7 of an accelerator pedal and an actual rotational speed D of an engine obtained by an engine rotational speed sensor 8 without using a throttle opening sensor for detecting the opening of the throttle valve 1.
NAKAMURA TOSHIAKI