Exhaust Gas Recirculation: Description and Operation

Fig. 52 Exhaust Gas Recirculation EGR System (std. CAL: A/T):

Fig. 53 Exhaust Gas Recirculation EGR System (HF):

The EGR system is designed to reduce oxides of nitrogen emissions (NOx) by recirculating exhaust gas through the EGR valve into the intake manifold and into the combustion chambers. It is composed of the EGR valve, Constant Vacuum Control (CVC) valve, EGR control solenoid valve, PGM-FI ECU and various sensors.
The ECU 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 ECU. The ECU 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 ECU cuts current to the EGR control solenoid valve to reduce vacuum applied to the EGR valve.