Exhaust Gas Recirculation: Description and Operation

System Diagram:

EGR System Outline
- The EGR system controls the oxides of nitrogen (NOx) emissions.
- Small amounts of exhaust gases are recirculated to the combustion chamber. The combustion chamber temperature is reduced and NOx emissions are lowered.
- The EGR control is enabled when the vehicle is running after warm up.
- The EGR control is cancelled when any of the following conditions are met.
- Engine is idling.
- During engine warm-up.
- Vehicle speed is below 3 km/h {2 mph}.
- Engine speed is below 1,000 rpm.
- Torque reduction control is activated. [KL engine only)
- Malfunction of ECT sensor, TP sensor, MAF sensor or EGR valve.

Block Diagram:

EGR System Monitor Outline
- The circuits of the EGR system devices are continuously monitored by the PCM.
- The EGR flow is monitored using the EGR boost sensor signal.

EGR System Component Part Description EGR valve
- The EGR valve is a stepping motor type.
- The PCM controls the EGR valve to increases or decreases the EGR amount.
- Engine coolant flows through the EGR valve to cool it and improve reliability. [KL engine only]




EGR Boost Sensor
- The EGR boost sensor converts the intake manifold pressure and barometric pressure into a voltage value, and sends the voltage signal to the PCM.
- The pressure application is changed by the EGR boost sensor solenoid valve.
- The voltage value is used only for the EGR and EVAP system monitoring.




EGR Boost Solenoid Valve
- The EGR boost solenoid valve switches the application of barometric pressure or intake manifold vacuum to the EGR boost sensor.
- Intake manifold vacuum is applied to the EGR boost sensor when the solenoid is energized.