Exhaust Gas Recirculation: Description and Operation

EGR System Operation:

Electronic EGR Transducer EET Location:

Fig. 1 Manifold Absolute Pressure (MAP) Sensor Location:

PURPOSE
The EGR system reduces emission of oxides of nitrogen (NOx).

OPERATION
The EGR solenoid is controlled by the PCM. When the PCM supplies a ground to the solenoid (energizing), vacuum is cut off from the EGR transducer

When the PCM removes the ground from the solenoid (de-energizing), vacuum is allowed to flow through the solenoid and out to the EGR transducer.

The PCM monitors engine coolant temperature and other operating conditions to determine when to energize the EGR solenoid.

Backpressure transducer varyies control vacuum to EGR valve, depending on pressure in exhaust system.

EGR valve control vacuum is ported vacuum, from the throttle body.

DIAGNOSTIC CHECK
The PCM checks system for failures. If a failure is detected, Malfunction Indicator Lamp is illuminated, (indicating immediate service is required).

The EGR solenoid disables system during diagnostic checks.

Lamp activated only during certain engine/driving conditions

THEORY
Inhibits the formation of NOx, by lowering the peak combustion temperature by mixing a metered amount of exhaust gas with incoming air/fuel mixture.

Often compared to adding wet wood to a fire

CONSTRUCTION
The system is consists of; the EGR Valve, EGR tube, (connects passage in the intake manifold to the exhaust manifold), backpressure transducer, EGR solenoid, wiring and connecting hoses.