Conditions for Setting the DTC: P0401
WARNING: This page is about a different car, the 2009 GMC Sierra, 2009 GMC Cab & Chassis Sierra, 2009 Chevrolet Silverado, and 2009 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The ECM detects that the difference between the actual mass air flow and the desired mass air flow is less than a calibrated value for greater than 15 seconds when the EGR is active.