Isuzu 2008MY N Series Workshop Manual page 398

Legend
1. Exhaust brake valve
2. Exhaust temperature sensor 2 (in front of oxygen
catalyst)
3. Exhaust temperature sensor 1 (in front of filter)
The DPD is a system that uses an oxidation catalyst to
clean the NOx and HC, and a filter to collect PM
discharged from the engine. When PM accumulated in
the filter, regeneration is performed. The ECM detects
the condition of PM accumulations from the exhaust
differential pressure sensor or from mileage. When it is
reached to a certain amount of PM accumulations or a
certain length of mileage, the automatic regeneration
starts. If the automatic regeneration cannot be
completed by some reason, the manual regeneration is
requested to the driver by blinking the DPD lamp on the
instrument panel cluster. During regeneration, the
temperature inside the filter is raised, and the
accumulated PM is burned off. In order to adjust to
optimized temperature, the ECM detects exhaust
temperature using the exhaust temperature sensors,
and then raises the temperature by controlling fuel
injections, the exhaust brake valve and exhaust throttle
valve to burn off the accumulated PM. Once the
regeneration starts, it must be finished within a certain
time. After regeneration is finished, a purification of the
filter is judged by monitoring the exhaust differential
pressure. If an excessive PM accumulation has been
detected, the regeneration will not start since
uncontrolled burning might be happened during
regeneration process.
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Engine Control System (4HK1)
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2
6
4. Exhaust differential pressure sensor
5. Exhaust throttle valve
6. DPD assembly
Exhaust Differnetial Pressure Sensor
The exhaust differential pressure sensor is attached to
the chassis frame near the DPD assembly. The
exhaust differential pressure sensor is a transducer
that varies voltage according to changes of the exhaust
gas differential pressure between in front and in rear of
DPD filter. The exhaust differential pressure sensor
provides a signal to the ECM on the signal circuit,
which is relative to the differential pressure changes in
front and in rear of DPD filter. The ECM should detect a
low signal voltage at a low differential pressure, such
as small PM accumulation. The ECM should detect
high signal voltage at high differential pressure, such as
large PM accumulation.
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5
1A-395
LNW76ESF000901
MFW4ADSH002301