Failure diagnosis apparatus for exhaust gas recirculation system

摘要

To provide a failure diagnosis apparatus for an exhaust gas recirculation system which is capable of eliminating the influence of various disturbance factors that vary the suction air pressure, diagnosing a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and preventing wrong diagnosis. A failure diagnosis apparatus for an exhaust gas recirculation system consists of a fresh air pressure estimating means 2911 for calculating an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine, an actual EGR (exhaust gas recirculation) gas pressure estimating means 2914 for estimating an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting means 2911 and an estimated fresh air pressure calculated above, and a failure judging means 2910 for judging the failure on the basis of the estimated EGR gas pressure and the detected operating condition.