Exhaust Gas Recirculation Systems: Overview
WARNING: This page is about a different car, the 2005 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.
The Exhaust Gas Recirculation (EGR) system controls the oxides of nitrogen (NOx) emissions. Small amounts of exhaust gases are recirculated back into the combustion chamber to mix with the air/fuel charge. The combustion chamber temperature is reduced, lowering NOx emissions.