What is the location of EGR valve and location of down stream o2 sensors.
The EGR valve is located on top of the engine. The downstream O2 Sensors are located after the catalytic converter.
EXHAUST GAS RECIRCULATION (EGR) SYSTEM DESCRIPTION
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 nitrogen oxides (NOx) is generated in the combustion chamber. Therefore, this system recirculates part of emission 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 dffect the driveability.
When the engine coolant temperature is low, the engine is at idle or when a wide open throttle operation is performed, the EGR valve is kept closed, allowing no EGR.
In normal vehicle operation, after the engine has warmed up, the EGR valve is opened to carry out EGR.
In addition, the engine control module monitors the EGR system and illuminates the check engine/malfunction indicator lamp to let the driver know that there is a malfunction.