Express 1/2 Ton Van V6-4.3L VIN W (1999)
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to lower Oxides of Nitrogen (NOx) emission levels caused by high combustion temperatures. It
accomplishes this by feeding small amounts of exhaust gases back into the combustion chamber. When the air/fuel mixture is diluted with the exhaust
gases, combustion temperatures are reduced.
A linear EGR valve is used on this system. The linear EGR valve is designed to accurately supply exhaust gases to the engine without the use of intake
manifold vacuum. The valve controls exhaust flow going into the intake manifold from the exhaust manifold through an orifice with a Control Module (
PCM/VCM) controlled pintle valve. The Control Module commands the EGR by applying a 12 volt duty cycle to the EGR valve. This can be monitored
on a scan tool as Desired EGR position.
