Conditions for Setting the DTC: P0121
WARNING: This page is about a different car, the 2010 GMC Sierra, 2010 GMC Cab & Chassis Sierra, and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The predicted air flow and the predicted MAP combined are outside a calibrated range for more than 3 seconds.