Exhaust Gas Recirculation: Description and Operation

GENERAL INFORMATION
The exhaust gas recirculation (EGR) system lowers the nitrogen oxide (NOx) emission level. When the air/fuel mixture combustion temperature is high, a large quantity of NOx is generated in the combustion chamber. Therefore, this system recirculates part of exhaust gas from the exhaust port of the cylinder head to the combustion chamber through the intake manifold to decrease the air/fuel mixture combustion temperature, resulting in reduction of NOx. The EGR flow rate is controlled by the EGR valve so as not to decrease the driveability.

OPERATION
When the engine coolant temperature is low, when the engine is at idle or when a wide open throttle operation is performed, the EGR valve is kept closed, achieving no EGR. After warming up of the engine, the EGR valve can be opened by the powertrain control module.
The powertrain control module monitors the EGR system and illuminates the check engine/malfunction indicator lamp to indicate that there is a malfunction.

System Diagram: