Exhaust Gas Recirculation: Description and Operation

- The EGR system is used to reduce oxides of nitrogen (NOx) emissions. The system recirculates a small portion of the exhaust gas into the intake manifold.

- The exhaust gas is non-combustible and takes up a small space in the intake charge. The result is lower combustion temperatures and reduced NOx.

- The opening and closing of the EGR valve is accomplished by supplying manifold pressure (vacuum) to the valve.

- An EGR Vacuum Regulator Solenoid Valve (N18), that is operated by the Engine Control Module (ECM), controls the amount of manifold pressure that is supplied to the EGR valve.

- By regulating the manifold pressure to the EGR valve, the amount of exhaust gas that is recirculated can accurately be controlled.

- The EGR Vacuum Regulator Solenoid valve is located on the rearward side of the right front shock tower under the air intake hose.

- The EGR system operates during the following conditions:

^ Engine speed between 1000 rpm and 4600 rpm
^ Engine load
^ Engine coolant temperature above 70°C (158°F)