Conditions For Setting DTC

WARNING: This page is about a different car, the 2003 GMC Sierra, 2003 GMC Cab & Chassis Sierra, 2003 Chevrolet Silverado, and 2003 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The ECM detects a calibrated difference between the expected MAF rate and the actual MAF rate during EGR system operation.
The ECM 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.