Exhaust Gas RECIRCULATION: Notes

The Exhaust Gas Recirculation (EGR) system is designed to reduce oxides of nitrogen (NOx) emissions by lowering combustion temperatures. This is accomplished when a metered amount of exhaust gas is recirculated into the intake manifold and mixed with the air/fuel mixture.

On PCM-controlled EGR systems using a solenoid, PCM controls manifold vacuum to EGR valve through solenoid valve. Solenoid is normally closed.

PCM uses engine coolant temperature, throttle position and manifold pressure signals to determine EGR operation. During cold engine operation and idle, EGR is not desired. To check EGR system, perform functional check of EGR system. See appropriate SYSTEM & COMPONENT TESTING article.