Exhaust Gas Recirculation: Description and Operation

Fig. 124 EGR System:

SYSTEM OPERATION

The EGR system introduces exhaust gases into the intake manifold to reduce the production of NOx. It operates depending on the engine load, engine speed (above 1,500 RPM), engine coolant temperature above 70°C (158°F). The EGR system consists of the following components: EGR control valve, EGR modulator valve, engine control unit, ignition coil, EGR solenoid valve, throttle sensor, engine coolant temperature sensor, and radiator coolant temperature sensor.

EGR CONTROL VALVE

The EGR control valve recirculates a portion of the exhaust gases.

EGR MODULATOR VALVE

The EGR modulator valve controls the vacuum acting on the EGR control valve.

EGR POSITION SENSOR (California only)

The EGR position sensor Detects EGR control valve lift amount; sent signal to control unit by means of a variable resistor incorporated on the top of the EGR valve.

ENGINE CONTROL UNIT

The engine control unit detects signals from input sensors and switches and controls the EGR solenoid valve.

EGR SOLENOID VALVE

The EGR solenoid valve controls the vacuum signal to the EGR control valve.