Subaru Legacy 2003 Service Manual page 555

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
ENGINE (DIAGNOSTICS)
5 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
Is there a fault in exhaust system?
NOTE:
Check the following items.
•Loose installation of portions
•Damage (crack, hole etc.) of parts
•Looseness and ill fitting of parts between front
oxygen (A/F) sensor and rear oxygen sensor
Step
EN(H4SO)-158
Value
There is a fault.
Yes
Repair or replace Replace rear oxy-
faulty parts. gen sensor. <Ref.
to FU(H4SO)-43,
Rear Oxygen Sen-
sor.>
No