Conditions For Setting DTC

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The PCM detects a calibrated difference between the expected MAF rate and the actual MAF rate during EGR system operation.
The PCM detects no difference between the expected EGR vacuum sensor signal and the actual EGR vacuum sensor signal.
The above conditions are met for more than 4 seconds.