FAILURE DIAGNOSTIC DEVICE FOR EGR SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a failure diagnostic device for an EGR system, that can accurately diagnose a failure in an EGR system regardless of the reflux destination of EGR gas refluxed from an exhaust passage to an intake passage.SOLUTION: A failure diagnostic device 101 for an EGR system 70 of an internal combustion engine 10 includes: an EGR pipe 61 connecting an exhaust passage 40 to an intake passage 20; an EGR valve 64 regulating the flow rate of the EGR gas flowing in the EGR pipe 61; and a differential pressure sensor 65 detecting a differential pressure Ps between the EGR gas on the exhaust passage 40 side of the EGR valve 64 and the EGR gas on the intake passage 20 side. The device diagnoses the failure of the EGR system 70 based on an exhaust pressure Pu of the EGR gas on the exhaust passage 40 side when the EGR valve 64 is closed, and the differential pressure Ps detected by the differential pressure sensor 65.