Subaru IMPREZA 2004 Service Manual page 440

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step
1 CHECK ANY OTHER DTC ON DISPLAY.
2 CHECK EXHAUST SYSTEM.
NOTE:
Check the following items.
•Loose installation of front portion of exhaust
pipe onto cylinder heads
•Loose connection between front exhaust pipe
and front catalytic converter
•Damage of exhaust pipe resulting in a hole
Check
Is any other DTC displayed?
Is there a fault in exhaust sys-
tem?
EN(H4SO)(diag)-131
ENGINE (DIAGNOSTICS)
Yes
Check DTC using Go to step 2.
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H4SO)(diag)-
74, List of Diag-
nostic Trouble
Code (DTC).>
NOTE:
In this case, it is
not necessary to
inspect
DTC P0133.
Repair exhaust Replace the front
system. oxygen (A/F) sen-
sor. <Ref. to
FU(H4SO)-43,
Front Oxygen (A/
F) Sensor.>
No