Subaru Impreza 2003 Service Manual page 537

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
6 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
•Loose installation of portions
•Damage (crack, hole etc.) of parts
•Looseness of front oxygen (A/F) sensor
•Looseness and ill fitting of parts between front
oxygen (A/F) sensor and rear oxygen sensor
Check
Is there a fault in exhaust sys-
tem?
EN(H4SO)-125
ENGINE (DIAGNOSTICS)
Yes
Repair or replace Replace the front
faulty parts. oxygen (A/F) sen-
sor. <Ref. to
FU(H4SO)-44,
Front Oxygen (A/
F) Sensor.>
No