The purpose of the exhaust gas recirculation (EGR) system is to reduce nitrogen oxide (NOx) emissions from the internal combustion engine. The EGR valve controls the exact amount of exhaust gas returned to the intake pipe. This reduces the amount of oxygen in the air supply to the cylinders, lowering the peak combustion temperature and reducing the formation of nitrogen oxides (NOx). This is particularly important for diesel engines.
A faulty EGR valve not only leads to a significant increase in nitrogen oxides (NOx) in the exhaust gas, but can also have a negative effect on other components, such as the particle filter.
