Exhaust Gas Recirculation: Description and Operation

DESCRIPTION AND OPERATION
The EGR system is designed to reduce oxides of nitrogen emissions (NOx) by recirculating exhaust gas through the EGR valve and the intake manifold into the combustion chambers. It is composed of the EGR valve, EGR vacuum control valve, EGR control solenoid valve, ECM/PCM and various sensors.
The ECM/PCM contains memories for ideal EGR valve lifts for varying operating conditions. The EGR valve lift sensor detects the amount of EGR valve lift and sends the information to the ECM/PCM. The ECM/PCM then compares it with the ideal EGR valve lift which is determined by signals sent from the other sensors. If there is any difference between the two, the ECM/PCM cuts current to the EGR control solenoid valve to reduce vacuum applied to the EGR valve.