Subaru Legacy 2003 Service Manual page 592

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)
Step
1 CHECK ANY OTHER DTC ON DISPLAY.
Is any other DTC displayed?
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.
Is there any fault in exhaust system?
NOTE:
Check the following positions.
•Between cylinder head and front exhaust pipe
•Between front exhaust pipe and front catalytic
converter
•Between front catalytic converter and rear cat-
alytic converter
3 CHECK CATALYTIC CONVERTER.
Is there any damage at catalyst?
4 CHECK REAR OXYGEN SENSOR CIRCUIT.
1) Disconnect rear oxygen sensor connector.
2) Measure the resistance between ECM and
rear oxygen sensor connector.
Connector & terminal
(B135) No. 19 - (T6) No. 3
Is the measured value less than the speci-
fied value?
5 CHECK SEALED WIRE.
Is the sealed wire connected?
Value
DTC indicated.
There is a fault.
There is a damage.
1 Ω
Connected.
EN(H4SO)-195
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
P0420.
Repair or replace Go to step 3.
exhaust system.
<Ref. to
EX(H4SO)-2, Gen-
eral Description.>
Replace front cat- Go to step 4.
alytic converter.
<Ref. to
EC(H4SO)-3,
Front Catalytic
Converter.>
Go to step 5. Repair open har-
ness between
ECM and rear oxy-
gen sensor.
Contact SUBARU Repair sealed
distributor service. wire.
NOTE:
Inspection by DTM
is required, be-
cause probable
cause is deteriora-
tion of multiple
parts.
No