Subaru Legacy 2005 Service Manual page 1900

Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step
1 CHECK FOR ANY OTHER DTC ON DIS-
PLAY.
2 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
rear oxygen sensor.
3) Measure the resistance of harness
between ECM and rear oxygen sensor con-
nector.
Connector & terminal
(B137) No. 24 — (E61) No. 3:
(B136) No. 35 — (E61) No. 4:
(B137) No. 25 — (E25) No. 3:
(B136) No. 35 — (E25) No. 4:
3 CHECK HARNESS BETWEEN REAR OXY-
GEN SENSOR AND ECM CONNECTOR.
Measure the resistance between rear oxygen
sensor harness connector and chassis ground.
Connector & terminal
(B137) No. 31 — Chassis ground:
4 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
5 CHECK CATALYTIC CONVERTER.
Check
Is any other DTC displayed?
Is the resistance less than 1
Ω?
Is the resistance less than 1
Ω?
Is there any fault in exhaust
system?
Is there damage at rear face or
front face of front catalytic con-
verter?
EN(H6DO)(diag)-204
Yes
Inspect the rele- Go to step 2.
vant DTC using
"List of Diagnostic
Trouble Code
(DTC)". <Ref. to
EN(H6DO)(diag)-
66, List of Diag-
nostic Trouble
Code (DTC).>
NOTE:
In this case, it is
not necessary to
inspect DTC
P0420.
Go to step 3. Repair open circuit
in harness
between ECM and
rear oxygen sen-
sor connector.
Go to step 4. Repair the open
circuit between
ECM and rear oxy-
gen sensor con-
nector.
Repair or replace Go to step 5.
the exhaust sys-
tem. <Ref. to
EX(H6DO)-2,
General Descrip-
tion.>
Replace the cata- Contact the SUB-
lytic converter. ARU dealer.
<Ref. to EC(H4SO
2.0)-3, Front Cata-
lytic Converter.>
No