Exhaust Gas Recirculation: Description and Operation

DESCRIPTION
The EGR System controls NOx by diluting the air/fuel mixture with exhaust gas. During specific engine operating modes, a small portion of exhaust gases are recirculated into the induction system. Since exhaust gases do not contain oxygen needed for the combustion process, the air/fuel ratio becomes less by volume. This lowers peak combustion temperatures, preventing NOx formation.


Exhaust Gas Recirculation (EGR) is regulated by a solenoid-type vacuum regulator device which is controlled by the Powertrain Control Module (PCM), based on return signals from various engine components, and the pressure transducer/sensor. Circuit power is supplied through the PCM power relay when circuit ground is provided internally by the PCM.

NOTE: This system is only on models with manual transmission. Other vacuum related components may be incorporated into the EGR system, depending on vehicle model and calibration.

OPERATION
Cold Engine (Coolant temperature is less than 55°C (131°F))
EGR operation is stopped to improve driveability when the engine temperature is cold.

Warm Engine
The PCM controls the EGR vacuum regulator solenoid to supply EGR gases.