Conditions for Setting the DTC

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 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.