Exhaust Gas Recirculation: Description and Operation

CIRCUIT DESCRIPTION
The EGR system recirculates exhaust gas, which is controlled to the proper quantity to suit the driving conditions, into the intake air mixture to slow down combustion, reduce the combustion temperature and reduce NOx emissions.
The lift amount of the EGR valve is controlled by a step motor operated by the ECM. The ECM operates the motor only a preprogrammed amount in response to the engine operating conditions (RPM, intake air volume to adjust the EGR volume to the target value.)
Under the following conditions, EGR is cut to maintain driveability.
- Before the engine is warmed up
- During deceleration (throttle valve closed)
- Light engine load (amount of intake air very small)
- Engine speed over 4,000 rpm
- Engine idling
- Park/neutral position switch ON