Subaru Legacy 2003 Service Manual page 569

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
14 CHECK CAUSE OF MISFIRE DIAGNOSED.
Was the cause of misfire diagnosed when the
engine is running?
NOTE:
Disconnected spark plug code, etc.
15 CHECK AIR INTAKE SYSTEM.
Is there any fault in air intake system?
Step
EN(H4SO)-172
Value
The cause of misfire found.
There is a fault.
Yes
Finish diagnostics (1) Repair poor
operation, if the contact.
engine has no
NOTE:
abnormality.
In this case, repair
the following:
• Poor contact
in ignitor con-
nector
• Poor contact
in ignition coil
connector
• Poor contact
in fuel injector
connector on
faulty cylinders
• Poor contact
in ECM connec-
tor
• Poor contact
in coupling con-
nector
(2) If there is no
poor contact, con-
tact SUBARU dis-
tributor. Before
contacting, the fol-
lowing items must
be checked:
• Fuel for con-
dition
• Fuel addi-
tives
• Spark plug
for condition
• Plug code for
condition
• Engine oil for
condition
Repair air intake Go to step 16.
system.
NOTE:
Check the follow-
ing items:
• Are there air
leaks or air suction
caused by loose or
dislocated nuts
and bolts?
• Are there cracks
or any disconnec-
tion of hoses?
No