DTC P0401 Or DTC P0402: Condition
WARNING: This page is about a different car, the 2002 Suzuki XL-7. However, it is still accessible from the selected car via links, so may be relevant.
DTC P0401 is set, when during deceleration difference in intake manifold absolute pressure value when EGR valve is opened, and when EGR valve is closed is less than specified value.
DTC P0402 is set, when during deceleration difference in intake manifold absolute pressure value when EGR valve is opened, and when EGR valve is closed is more than specified value. MIL is illuminated when ECM detects malfunction during 2 consecutive drive cycles.