Subaru Legacy 2003 Service Manual page 546

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK ANY OTHER DTC ON DISPLAY.
Is any other DTC displayed?
2 CHECK EXHAUST SYSTEM.
Is there a problem in 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
Value
DTC indicated.
There is a problem.
EN(H4SO)-149
ENGINE (DIAGNOSTICS)
Yes
Inspect the rele- Go to step 2.
vant DTC using
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H4SO)-83, List
of Diagnostic
Trouble Code
(DTC).>
NOTE:
In this case, it is
not necessary to
inspect DTC
P0133.
Repair exhaust Replace front oxy-
system. gen (A/F) sensor.
<Ref. to
FU(H4SO)-41,
Front Oxygen (A/
F) Sensor.>
No