Subaru Impreza 2003 Service Manual page 1317

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
6 CHECK EXHAUST SYSTEM.
Check the exhaust system parts.
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
Check
Is there a fault in exhaust sys-
tem?
EN(H4DOTC)-141
ENGINE (DIAGNOSTICS)
Yes
Repair or replace Replace the rear
the faulty parts. oxygen sensor.
<Ref. to
FU(H4DOTC)-46,
Rear Oxygen Sen-
sor.>
No