The Exhaust Gas Recirculation (EGR) system lowers the NOx (Oxides of Nitrogen) emission levels created by the high combustion temperatures. The main element of the system is an EGR valve.

On the vehicles that are equipped with California emissions, most applications use a linear EGR valve and a canister purge solenoid.

The EGR valve will open when the conditions of operation have been met. This allows the exhaust gasses to re-enter the combustion chamber. When too much exhaust gas is allowed to enter the chamber, the proper combustion will not occur. For this reason, only very little exhaust gas is allowed to re-enter the combustion chamber.