Conditions for Setting the DTC
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2011 GMC Yukon XL, 2011 GMC Yukon, 2011 Chevrolet Tahoe, 2011 Chevrolet Suburban, and 2011 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
P0068
The ECM detects that the throttle position and the indicated engine load do not correspond with the expected load and throttle position for less than 1 second.
P0121
The predicted air flow and the predicted MAP combined are outside a calibrated range for more than 3 seconds.