Exhaust Gas Recirculation (EGR) System: Overview
WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
The EGR system controls 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 thereby reduced, lowering NOx emissions.