Conditions for Setting the DTC: P2271
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 does not detect an HO2S voltage less than 150 mV before accumulated mass air flow exceeds 550 grams.