Subaru Legacy 2004 Service Manual page 586

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK ANY OTHER DTC ON DISPLAY.
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.
NOTE:
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 converter
3 CHECK CATALYTIC CONVERTER.
4 CHECK REAR OXYGEN SENSOR GROUND
HARNESS.
1) Disconnect the rear oxygen sensor and
ECM connectors.
2) Measure the resistance between rear oxy-
gen sensor connector and ECM connector.
Connector & terminals
(B19) No. 3 — (B136) No. 18:
5 CHECK SHIELD HARNESS.
Check
Is any other DTC displayed?
Is there any fault in exhaust
system?
Is there damage at rear face or
front face of front catalyst?
Is the resistance less than 1
&?
Is the shield harness opened? Repair the shield
EN(H4SO 2.0)(diag)-154
Yes
Inspect the rele- Go to step 2.
vant DTC using
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H4SO
2.0)(diag)-66, List
of Diagnostic Trou-
ble Code (DTC).>
NOTE:
In this case, it is
not necessary to
inspect DTC
P0420.
Repair or replace Go to step 3.
the exhaust sys-
tem. <Ref. to
EX(H4SO 2.0)-2,
General Descrip-
tion.>
Replace the cata- Go to step 5.
lytic converter.
<Ref. to EC(H4SO
2.0)-3, Front Cata-
lytic Converter.>
Go to step 5. Repair the open
circuit in harness
between ECM and
rear oxygen sen-
sor.
Contact with your
harness. Subaru distributor
service.
No