Subaru Legacy 2004 Service Manual page 571

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
15 CHECK AIR INTAKE SYSTEM.
16 CHECK MISFIRE SYMPTOM.
1) Turn the ignition switch to ON.
2) Read the DTC.
• Subaru Select Monitor
<Ref. to EN(H4SO 2.0)(diag)-25, Subaru
Select Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to
OBD-II General Scan Tool Operation Manual.
NOTE:
Perform diagnosis according to the items listed
below.
17 CHECK DIAGNOSTIC TROUBLE CODE
(DTC) ON DISPLAY.
Is any other DTC displayed?
18 CHECK DIAGNOSTIC TROUBLE CODE
(DTC) ON DISPLAY.
Is any other DTC displayed?
19 CHECK DIAGNOSTIC TROUBLE CODE
(DTC) ON DISPLAY.
Is any other DTC displayed?
20 CHECK DIAGNOSTIC TROUBLE CODE
(DTC) ON DISPLAY.
Is any other DTC displayed?
21 ONLY ONE CYLINDER
Check
Is there any fault in air intake
system?
Does the Subaru Select Moni-
tor or OBD-II general scan tool
display only one DTC?
Does the Subaru Select Moni-
tor or OBD-II general scan tool
indicate DTC P0301 and
P0302?
Does the Subaru Select Moni-
tor or OBD-II general scan tool
indicate DTC P0303 and
P0304?
Does the Subaru Select Moni-
tor or OBD-II general scan tool
indicate DTC P0301 and
P0303?
Does the Subaru Select Moni-
tor or OBD-II general scan tool
indicate DTC P0302 and
P0304?
Is there any fault in that cylin-
der?
EN(H4SO 2.0)(diag)-139
ENGINE (DIAGNOSTICS)
Yes
Repair the air Go to step 16.
intake 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?
Go to step 21. Go to step 17.
Go to step 22. Go to step 18.
Go to step 23. Go to step 19.
Go to step 24. Go to step 20.
Go to step 25. Go to step 26.
Repair or replace Go to DTC P0171.
faulty parts. <Ref. to EN(H4SO
2.0)(diag)-126,
NOTE:
DTC P0171 SYS-
Check the follow-
TEM TOO LEAN
ing items.
(BANK 1), Diag-
• Spark plug
nostic Procedure
• Spark plug cord
with Diagnostic
• Fuel injector
Trouble Code
• Compression
(DTC).>
ratio
No