Isuzu 4JA1 Workshop Manual page 360

6E-106 Engine Control System (4JH1)
Step
3 1. Inspect the following for possible causes of high
boost pressure.
•
Wastegate
condition. Refer to the Turbocharger in
Engine Mechanical section for diagnosis.
•
Restricted intake or collapsed hose.
2. Repair the condition as necessary.
Did you find and correction the condition?
4 1. Turn OFF the ignition for 30 seconds.
2. Start the engine and warm up (allow engine
coolant temperature to reach at least 60°C
[140°F]).
3. Perform the EGR Solenoid Valve test with the
scan tool.
4. Command the EGR Solenoid Valve ON and OFF
with the scan tool while observing the Mass Air
Flow (MAF) Sensor parameter.
Does the MAF Sensor parameter decrease by at
least 200 mg/strk within 2 seconds when the EGR
Solenoid Valve is commanded ON?
5 1. Turn OFF the ignition.
2. Inspect for the following conditions:
•
An EGR valve control vacuum hose is
damaged or kinked.
•
EGR solenoid valve vacuum hoses are
damaged or kinked.
•
EGR solenoid valve ventilation is damaged.
•
An EGR valve is stuck close.
•
Restricted or collapsed EGR passage
between the exhaust manifold and EGR
valve.
•
Oil in the air tubing causing an incorrect
MAF
adhesion of oil, inside of the tubing,
intercooler and turbocharger needs to be
wipe off.
•
Contaminated or skewed MAF sensor.
3. Repair or replace as necessary.
Did you find and correct the condition?
6 1. Turn OFF the ignition.
2. Disconnect the EGR valve control vacuum hose
from the EGR valve.
3. Connect a hand-held vacuum pump (5-8840-
0279-0/J-23738-A) to the disconnected vacuum
hose.
4. Start the engine and let engine idle.
5. Perform the EGR Solenoid Valve test with the
scan tool.
6. Command the EGR Solenoid Valve ON and OFF
with the scan tool.
Does the hand-held vacuum pump indicate more
than 50 cmHg (20 inHg) when commanding the ON
and less than 10 cmHg (4 inHg) when commanding
OFF?
Action
valve for a stuck closed
sensor signal. When
Value(s)



there is

Yes
Go to Step 11 Go to Step 4
Go to Diagnostic
Aids Go to Step 5
Go to Step 11 Go to Step 6
Go to Step 7 Go to Step 10
No