A <Model> EGR valve (Exhaust Gas Recirculation) is fitted to reduce your car's Nitrogen Oxide emissions. It does this by recirculating some of the engine's exhaust gas back into the engine as this helps to reduce the combustion temperature and therefore the amount of NOx produced by the engine.
The <Model> EGR valve is located between the exhaust and inlet manifold usually on the back of the engine.
The EGR valve is responsible for recirculating or re directing exhaust gases back into the engine through the inlet manifold. The <Model> EGR valve is generally controlled or regulated by pressure or VAC lines to ensure that it is opened and closed at the correct time.
Your EGR valve can stop working due to leaks in the VAC lines, blockage due to soot deposits or failure of the actuator/control mechanism.