Isuzu 2008MY N Series Workshop Manual page 394

The EGR system recirculates a part of exhaust gas
back into the intake manifold, which results in reducing
nitrogen oxide (NOx) emissions. The EGR control
system uses an electronic control system to ensure
both driveability and low emission. A control current
from the ECM operates a solenoid to control the lift
amount of EGR valve. Also, EGR position sensors are
provided at the rear of the motor to feed actual valve lift
amount back to the ECM for more precision control of
the EGR amount.
The EGR control starts when the conditions for engine
speed, engine coolant
temperature and barometric pressure are satisfied.
Then, the valve opening is calculated according to the
engine speed, and target fuel injection quantity. Based
on this valve opening, the drive duty of the solenoid is
provided and the valve is driven accordingly. The intake
throttle valve is provided to adequate intake manifold
depression to ensure EGR gas flow.
EGR Valve
The EGR valve is mounted on the intake manifold. The
ECM controls the EGR valve opening based on the
engine running condition. The ECM controls the EGR
valve by controlling the solenoid. The solenoid is
controlled based on pulse width modulation (PWM)
signal sent from the ECM. The EGR valve position is
detected by the position sensor, and relayed to the
ECM. The position sensor is made up three individual
sensors within one housing. The EGR position sensor
1, 2 and 3 are hall element type sensors. The position
sensor provides a low or high signal state to the ECM
on the signal circuits, which is relative to the position
changes of the EGR valve.
temperature, intake
LNW76ESH002901
Engine Control System (4HK1)
Intake Throttle Valve
air
The intake throttle valve is located on the intake
manifold inlet. The ECM controls the intake throttle
valve opening based on the engine running condition.
The ECM controls the intake throttle valve by
controlling the solenoid. The solenoid is controlled
based on pulse width modulation (PWM) signal sent
from the ECM. A duty ratio change 0% to appropriate
percentage is intake throttle valve opening angle
control. To open the valve, duty ratio is increased. To
close the valve, duty ratio becomes small.
The intake throttle valve position is detected by the
position sensor, and relayed to the ECM. The position
sensor provides a signal to the ECM on the signal
circuit, which is relative to the position changes of the
intake throttle valve. The ECM should detect a low
signal voltage at a small opening amount or closed
position. The ECM should detect high signal voltage at
a large opening amount.
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