California

PURPOSE
Exhaust gas recirculation reduces oxides of nitrogen emissions in the vehicle exhaust. The EGR system uses partial recirculation of exhaust gases from a port in the cylinder head to a port in the intake manifold to lower combustion chamber temperature.

OPERATION
When the engine control module determines conditions are suitable for EGR operation it disconnects the ground supply to the solenoid. This allows the solenoid to connect the inlet and outlet ports, allowing ported manifold vacuum to be applied to the EGR valve diaphragm. The EGR valve controls the flow of exhaust gas in response to ported vacuum. At partial throttle settings ported vacuum is high and the EGR valve is open. At full throttle and idle port vacuum is low and the EGR valve remains closed. The EGR system is also equipped with a temperature sensor in the passage (for self-diagnostic purposes). It is used to signal the engine control module when the EGR valve is operating.