EGR Fault Detection
WARNING: This page does not describe the selected car, but rather 33 other vehicles, including the 2002 Saturn Vue, 2002 Pontiac Montana, 2002 Pontiac Aztek, 2002 Oldsmobile Silhouette, and 2002 Oldsmobile Bravada. However, it is still accessible from the selected car via links, so may be relevant.
The PCM uses input from the MAP sensor to measure amount of absolute pressure in EGR vacuum line. If a minor variation between calculated EGR and actual EGR is monitored by PCM, necessary corrections are made by the PCM. If variation is too great for PCM to correct, an error is detected. The PCM then enters into a default mode and sets a related diagnostic trouble code in memory.