Subaru IMPREZA 2004 Service Manual page 74

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
25 GROUP OF #2 AND #4 CYLINDERS
26 CYLINDER AT RANDOM
Check
Are there faults in #2 and #4
cylinders?
Is the engine idle rough?
EN(H4SO)(diag)-151
ENGINE (DIAGNOSTICS)
Yes
Repair or replace Go to DTC P0171.
faulty parts. <Ref. to
EN(H4SO)(diag)-
NOTE:
141, DTC P0171
Check the follow-
SYSTEM TOO
ing items.
LEAN (BANK 1),
• Spark plugs
Diagnostic Proce-
• Fuel injectors
dure with Diagnos-
• Compression
tic Trouble Code
ratio
(DTC).>
• Skipping timing
belt teeth
Go to DTC P0170. Repair or replace
<Ref. to faulty parts.
EN(H4SO)(diag)-
NOTE:
141, DTC P0171
Check the follow-
SYSTEM TOO
ing items.
LEAN (BANK 1),
• Spark plugs
Diagnostic Proce-
• Fuel injectors
dure with Diagnos-
• Compression
tic Trouble Code
ratio
(DTC).>
No