US Patent 7131321 Throttle system abnormality determination apparatus

An abnormality determination apparatus of a throttle control system calculates an integrated value of a deviation between an actual throttle angle and a target throttle angle. The abnormality determination apparatus determines existence or nonexistence of an abnormality in the throttle control system by comparing the integrated value with an abnormality determination value. The abnormality determination value is changed so that the abnormality determination value becomes smaller in a low-speed traveling period than in a high-speed traveling period. Thus, in the low-speed traveling period, in which an influence of the abnormality in the throttle control system on an operating state of an engine becomes larger than in the high-speed traveling period, the abnormality in the throttle control system can be detected and failsafe processing can be started in an early stage of the abnormality.