catalytic SUBARU FORESTER 2004 Service Owner's Manual

EN(H4DOTC)-187
ENGINE (DIAGNOSTIC)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK ANY OTHER DTC ON DISPLAY.Is any other DTC displayed? Inspect the rele-
vant DTC using
“List of Diagnostic
Trouble Code
(DTC)”. EN(H4DOTC)-74,
List of Diagnostic
Trouble Code
(DTC).>
N
OTE:
In this case, it is
not necessary to
inspect DTC
P0420.Go to step 2.
2 CHECK EXHAUST SYSTEM.
Check for gas leaks or air suction caused by
loose or dislocated nuts and bolts, and open
hole at exhaust pipes.
N
OTE:
Check the following positions.
 Between cylinder head and front exhaust
pipe
 Between front exhaust pipe and front cata-
lytic converter
 Between front catalytic converter and rear
catalytic converterIs there a fault in exhaust sys-
tem?Repair or replace
the exhaust sys-
tem. EX(H4DOTC)-2,
General Descrip-
tion.>Go to step 3.
3 CHECK REAR CATALYTIC CONVERTER.
Separate rear catalytic converter from rear
exhaust pipe.Is there damage at rear face of
rear catalyst?Replace the front
and rear catalytic
converter EC(H4DOTC)-3,
Front Catalytic
Converter.> to EC(H4DOTC)-4,
Rear Catalytic
Converter.>Go to step 4.
4 CHECK FRONT CATALYTIC CONVERTER.
Remove the front catalytic converter.Is there damage at rear face or
front face of front catalyst?Replace the front
catalytic con-
verter. EC(H4DOTC)-3,
Front Catalytic
Converter.>Contact the SUB-
ARU dealer.
NOTE:
Inspection by DTM
is required, be-
cause probable
cause is deteriora-
tion of multiple
parts.

EN(H4DOTC 2.5)-11
ENGINE (DIAGNOSTIC)
Electrical Component Location
(1) Front oxygen (A/F) sensor (3) Exhaust gas temperature sensor (5) Rear oxygen sensor
(2) Precatalytic converter (4) Front catalytic converter (6) Rear catalytic converter
EN-02351 (1)
(5)
(6)
(4)
(2)(3)