Isuzu 2008MY N Series Workshop Manual page 174

Step
1. Inspect the following conditions:
• An EGR valve gasket that is missing or
damaged
• A sticking EGR valve
• EGR gas leakage from any of the EGR
passages between the exhaust manifold
and intake manifold
• Restricted or collapsed EGR passage
between the exhaust manifold and the
EGR valve
• Any type of restriction in the exhaust
system
• Restricted air cleaner element, restricted
or collapsed air tubing between the air
cleaner and the intake manifold
4
• Any air induction leak
• Any water intrusion in the induction
system
• Any contamination or objects that block
the MAF sensor inlet
• Skew or slow MAF sensor
• Exhaust throttle valve or exhaust brake
valve for stuck condition. Refer to
Exhaust System in Section 1G Engine
Exhaust.
• A ventilation duct that is connected to the
exhaust tail pipe. Retest without the duct
if connected.
2. Repair or replace as necessary.
Did you find and correct the condition?
1. Perform the EGR Solenoid Control with a scan
tool several times.
2. Command the Desired EGR Position Increase
and Decrease while observing the EGR
5
Position 1.
Does the EGR Position 1 parameter follow
within the specified value quick enough
(compare with a similar unit if available)?
Replace the EGR valve. Refer to EGR Valve and
EGR Cooler in Section 1F Emission Control.
6
Did you complete the replacement?
1. Reconnect
harness connector(s).
2. Clear the DTCs with a scan tool.
Notice: A history DTC will not clear.
3. Turn OFF the ignition for 30 seconds.
7
4. Start the engine and warm up (allow engine
coolant temperature to reach at least 75°C
[167°F])
5. Let idle for at least 3 minutes while observing
the DTC Information with a scan tool.
Did the DTC fail this ignition?
Action
all previously disconnected
Engine Control System (4HK1)
Value(s) Yes
—
Go to Step 7
± 5%
Go to Diagnostic
Aids
—
Go to Step 7
—
Go to Step 2
1A-171
No
Go to Step 5
Go to Step 6
Go to Step 8