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The EGR solenoid valve which is incorporated in the emission control solenoid assembly
is a duty solenoid valve.
The engine-ECU controls the vacuum of the EGR valve to change the induction amount of
EGR by actuating this solenoid valve.
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The EGR cooler solenoid valve which is incorporated in the emission control solenoid assembly
is an ON/OFF solenoid valve.
The engine-ECU actuates this solenoid valve to open and close the exhaust flap which allows
the EGR to flow or not to flow through the EGR cooler.
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The exhaust flap remains in the open position up to a engine coolant temperature of 35°C
and exhaust gas does not pass through the EGR cooler.
In this way, the catalytic converter and the engine reach their operating temperatures
within the short space of time. The hydrocarbon, carbon monoxide and particulate emissions are reduced
as a result.
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From a engine coolant temperature of 35°C, the exhaust flap is closed by the
changeover valve.
The recirculated exhaust gas now flows through the EGR cooler. This helps to further reduce NOx.
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