egr system of an internal combustion engine

A failure diagnosis of the EGR apparatus implemented accurately and sufficiently to provide an EGR system kept high internal combustion engine capable diagnostic accuracy of the EGR device. When the opening degree of the intake air flow control valve is limited to a predetermined opening degree by A fuel cut actuates the EGR apparatus, an EGR device based on the change of the intake manifold pressure after the operation and prior to actuation of the EGR device While diagnosing the failure (S48), when not carrying out the manifold negative pressure moderately sum control, correct for changes in intake manifold pressure in the change of the first reference intake pressure varies according to the engine rotational speed Ne (P (Ne)) and (S26), whereas, when carrying out the intake manifold negative pressure moderately sum control to compensate for changes in intake manifold pressure in the change of the second reference intake pressure which changes according to the engine rotational speed Ne (PL (Ne)) (S40 ). .The