Subaru 2009 IMPREZA Service Manual page 601

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
20 ONLY ONE CYLINDER.
21 GROUP OF #1 AND #2 CYLINDERS.
22 GROUP OF #3 AND #4 CYLINDERS.
Check
Is there any fault in the cylin-
der?
Are there any faults in #1 and
#2 cylinders?
Are there any faults in #3 and
#4 cylinders?
EN(H4SO)(diag)-184
Yes No
Repair or replace Go to DTC P0171.
faulty parts. <Ref. to
EN(H4SO)(diag)-
NOTE:
161, DTC P0171
Check the follow-
SYSTEM TOO
ing items.
LEAN (BANK 1),
• Spark plug
Diagnostic Proce-
• Spark plug cord
dure with Diagnos-
• Fuel injector
tic Trouble Code
• Compression ra-
(DTC).>
tio
Repair or replace Go to DTC P0171.
faulty parts. <Ref. to
EN(H4SO)(diag)-
NOTE:
161, DTC P0171
• Check the fol-
SYSTEM TOO
lowing items.
LEAN (BANK 1),
• Spark plug
Diagnostic Proce-
• Fuel injector
dure with Diagnos-
• Ignition coil
tic Trouble Code
• Compression
(DTC).>
ratio
• If any fault are
not found, check
the "IGNITION
CONTROL SYS-
TEM" of #1 and #2
cylinders side.
<Ref. to
EN(H4SO)(diag)-
76, IGNITION
CONTROL SYS-
TEM, Diagnostics
for Engine Starting
Failure.>
Repair or replace Go to DTC P0171.
faulty parts. <Ref. to
EN(H4SO)(diag)-
NOTE:
161, DTC P0171
• Check the fol-
SYSTEM TOO
lowing items.
LEAN (BANK 1),
• Spark plug
Diagnostic Proce-
• Fuel injector
dure with Diagnos-
• Ignition coil
tic Trouble Code
• Compression
(DTC).>
ratio
• If any fault are
not found, check
the "IGNITION
CONTROL SYS-
TEM" of #3 and #4
cylinders side.
<Ref. to
EN(H4SO)(diag)-
76, IGNITION
CONTROL SYS-
TEM, Diagnostics
for Engine Starting
Failure.>