Subaru Legacy 2003 Service Manual page 571

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
22 GROUP OF #1 AND #2 CYLINDERS
Are there faults in #1 and #2 cylinders?
23 GROUP OF #3 AND #4 CYLINDERS
Are there faults in #3 and #4 cylinders?
24 GROUP OF #1 AND #3 CYLINDERS
Are there faults in #1 and #3 cylinders?
Step
EN(H4SO)-174
Value
There are faults.
There are faults.
There are faults.
Yes
Repair or replace Go to DTC P0171.
faulty parts. <Ref. to
EN(H4SO)-162,
NOTE:
DTC P0171 —
• Check the fol-
SYSTEM TOO
lowing items.
LEAN (BANK 1) —
• Spark plugs
, Diagnostic Pro-
• Fuel injectors
cedure with Diag-
• Ignition coil
nostic Trouble
• Compres-
Code (DTC).>
sion ratio
• If no abnormal is
discovered, check
for "IGNITION
CONTROL SYS-
TEM" of #1 and #2
cylinders side.
<Ref. to
EN(H4SO)-72,
IGNITION CON-
TROL SYSTEM,
Diagnostics for
Engine Starting
Failure.>
Repair or replace Go to DTC P0171.
faulty parts. <Ref. to
EN(H4SO)-162,
NOTE:
DTC P0171 —
• Check the fol-
SYSTEM TOO
lowing items.
LEAN (BANK 1) —
• Spark plugs
, Diagnostic Pro-
• Fuel injectors
cedure with Diag-
• Ignition coil
nostic Trouble
• If no abnormal is
Code (DTC).>
discovered, check
for "16. D: IGNI-
TION CONTROL
SYSTEM" of #3
and #4 cylinders
side. <Ref. to
EN(H4SO)-72,
IGNITION CON-
TROL SYSTEM,
Diagnostics for
Engine Starting
Failure.>
Repair or replace Go to DTC P0171.
faulty parts. <Ref. to
EN(H4SO)-162,
NOTE:
DTC P0171 —
Check the follow-
SYSTEM TOO
ing items.
LEAN (BANK 1) —
• Spark plugs
, Diagnostic Pro-
• Fuel injectors
cedure with Diag-
• Skipping timing
nostic Trouble
belt teeth
Code (DTC).>
No