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The EGR valve is mounted at the exhaust manifold side of cylinder head. The EGR valve
has the integrated motor that changes the opening degree of the exhaust gas induction valve to
control the amount of the exhaust gas recirculation.
The engine-ECU controls the EGR valve by changing the electrical currents going through
the motor coil.
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The EGR valve position sensor is installed in the EGR valve.
EGR valve position sensor outputs voltage to engine-ECU based on the EGR valve opening
angle.
Engine-ECU uses this signal to detect degree of the EGR valve opening.
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The EGR cooler solenoid valve which is mounted at the inlet manifold side of cylinder
head via the bracket is an ON/OFF control type solenoid valve.
The engine-ECU actuates this solenoid valve to open and close the EGR cooler by-pass valve
which allows the EGR to flow or not to flow through the EGR cooler.
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When the engine coolant is at low temperatures, the EGR cooler solenoid valve is in the
ON position. The EGR cooler by-pass valve closes the passage at the EGR cooler side and opens
the by-pass passage in order that the exhaust gas cannot flow 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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When the engine coolant is higher than the specified temperatures, the EGR cooler solenoid
valve is in the OFF position. The EGR cooler by-pass valve opens the passage at the EGR cooler
side and closes the by-pass passage in order that the exhaust gas can flow through the EGR cooler.
The recirculated exhaust gas now flows through the EGR cooler. This helps to further reduce
NOx.
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