Isuzu 2008MY N Series Workshop Manual page 289

1A-286 Engine Control System (4HK1)
Step
1. Inspect the following for possible causes of
low exhaust differential pressure.
• Misrouted
differential pressure hoses or pipes
Important:
directionality in the exhaust differential
pressure
System in Section 1G Engine Exhaust .
• Plugged, crushed or kinked exhaust
differential pressure hoses or pipes
• Dislocated or inclined exhaust differential
pressure
System in Section 1G Engine Exhaust .
• Physical
differential pressure sensor
• Any contamination or objects that block
the exhaust differential pressure sensor
3
port
• Skewed or slow exhaust differential
pressure sensor
• An exhaust system gasket that is missing
or damaged
• Exhaust gas leakage from the exhaust
pipe, gasket, DPD assembly, exhaust
temperature
differential pressure hoses or pipes
• Modified exhaust system
• Exhaust throttle valve or exhaust brake
valve for stuck condition. Refer to
Exhaust System in Section 1G Engine
Exhaust.
2. Repair or replace as necessary.
Did you find and correct the condition?
1. Remove the DPD filter from the DPD
assembly. Refer to Exhaust Pipe in Section
1G Engine Exhaust.
2. Inspect the DPD filter for damage, cracks or
melt.
3. Inspect the oxygen catalyst for damage or
excessive deposits.
4
Important: DPD status in the ECM must be
reset when the DPD filter is replaced.
4. Replace the DPD filter or the oxygen catalyst
as necessary. Refer to Exhaust Pipe in
Section 1G Engine Exhaust.
Did you find and correct the condition?
Action
or disconnected exhaust
There is installation
hoses. Refer to Exhaust
sensor. Refer to Exhaust
damage of the exhaust
sensor(s) or exhaust
Value(s) Yes
—
Go to Step 7
—
Go to Step 7
No
Go to Step 4
Go to Step 5