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25-6EMISSION CONTROL SYSTEMS- Exhaust Gas Recirculation (EGR) System
OPERATION
The engine control unit functions to calculate the
engine load, based upon the intake air volume
signals (from the air-flow sensor) and the rpm
signals (from the crank-angle sensor), and the
EGRcontrol solenoid valve is activated according to the
engine load. The
EGR amount is then regulated
according to the engine load calculated in this way.maintaining driveability during cold.
When, as a result of clogging of the
EGR cant’valve or as a result of an operational
malfunctio,.,the
EGR flow volume decreases, the EGR gas
temperature downstream. from the
EGR control
valve decreases. The engine control unit functions
to detect the
operation conditions of the EGRLoad
a Intake air volume/Engine rpmsystem by this characteristic.
If, however, the engine coolant temperature is low,
the actuation duty is attenuated, the
EGR control
valve activation negative pressure (vacuum) is
leaked from the throttle body A port, thus reducing
or interrupting the
EGR flow volume and therebyThe temperature of the
EGR gas is detected by the
EGR gas temperature sensor which is equipped at
the
EGR control valve; when the temperature
decreases to a low level, the engine warning light
(malfunction indicator light) illuminates in order to
advise the driver that a malfunction has occurred in
the
EGR system.
EGR
contcEGR control
solenoid valve
/Control
relay
1Engine control unit
Enginewarning
light
