Conditions For Setting DTC

WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 GMC Savana Special, 2002 GMC Savana Camper Special, and 2002 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.

The PCM detects that the difference between the actual airflow (MAF) and the Speed Density calculated air flow is greater than expected.
All of the above conditions met for less than 1 second.