Outline Of Diagnosis
WARNING: This page is about a different variant/trim than selected.
Detect the malfunction of EGR system.
Intake manifold pressure is constant because the throttle valve is fully closed during deceleration fuel cut.
At this time, when the EGR control valve is opened/closed, the intake manifold pressure will change. The ECM compares the difference between the intake manifold pressure assumed at the time of EGR control valve opening or closing command and the actually measured intake manifold pressure to judge whether the EGR system is normal/over flow rate/under flow rate.