Exhaust Gas RECIRCULATION (EGR)
WARNING: This page is about a different car, the 2018 Jaguar XE and 2017 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.
The Exhaust Gas Recirculation (EGR) reduces the oxides of nitrogen (NOX) emissions from the engine by passing the exhaust gases back through the engine via the intake manifold.
This reduces the amount of oxygen in the intake air which reduces the creation of NOX as part of the combustion process.
NOx is formed by the naturally occurring Nitrogen in the air and the oxygen burning at high temperatures. By recirculating the exhaust gasses the ignition temperature in the engine is reduced, reducing the production of NOx.