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ENGINE AND EMISSION CONTROL - Emission Control System 17-13 EXHAUST GAS RECIRCULATION (EGR) SYSTEM 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 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 decrease the driveability. OPERATION The EGR valve is being closed and does not recirculate exhaust gases under one of the following conditions. Otherwise, the EGR valve is opened and recirculates exhaust gases. D The engine coolant temperature is low. D The engine is at idle. D The throttle valve is widely opened. SYSTEM DIAGRAM ON Throttle body EGR control solenoid valve Engine control relay Battery EGR valve Crank angle sensor Throttle position sensor Engine-ECU Engine coolant temperature sensor Air flow sensor |