Patent ID: 7104259

Claim:
A diagnostic device for an exhaust gas recirculation apparatus with an EGR valve disposed in a recirculation pipe interconnecting an exhaust pipe and an intake pipe downstream of a throttle valve, comprising: EGR control means for selectively executing an EGR on-control to return an exhaust gas from said exhaust pipe to said intake pipe and an EGR off-control to cut off said return of said exhaust gas from said exhaust pipe to said intake pipe; diagnostic means for diagnosing a failure of said EGR system based on an intake pipe pressure during said EGR on-control and an intake pipe pressure during said EGR off-control when a diagnosis run condition is satisfied; and cancellation means for canceling diagnosis executed by said diagnostic means when said intake pipe pressure during the EGR off-control exceeds a presetted cancel determination value so as to easily and precisely perform to diagnose said failure.