Page 1344 of 2453
EN(H6DO)(diag)-183
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
5 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following item.
•Loose part and incomplete installation of ex-
haust system
•Damage (crack, hole etc.) of parts
•Looseness and ill fitting of parts between
front oxygen (A/F) sensor and rear oxygen sen-
sor
Is there any fault in exhaust
system?
Repair or replace
faulty par ts.
Replace the rear
oxygen sensor.
FU(H6DO)-30,
Rear Oxygen Sen-
sor.>
Step Check Yes No
Page 1347 of 2453

EN(H6DO)(diag)-186
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK ANY OTHER DTC ON DISPLAY.Is any other DTC displayed? Check DTC using
“List of Diagnostic
Tr o u b l e C o d e
(DTC)”.
EN(H6DO)(diag)-
69, List of Diag-
nostic Trouble
Code (DTC).>
NOTE:
In this case, it is
not necessary to
inspect DTC
P0139.
Go to step 2.
2CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness
between ECM and rear oxygen sensor con-
nector.
Connector & terminal
(B135) No. 4 — (E61) No. 3:
Is the resistance less than 1
Ω?
Go to step 3.Repair the open
circuit of harness
between ECM and
rear oxygen sen-
sor connector.
3CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
Measure the resistance between rear oxygen
sensor harness connector and chassis ground.
Connector & terminal
(E61) No. 3 — Chassis ground
Is the resistance more than 1
MΩ?
Go to step 4.Repair the chas-
sis short circuit of
harness.
4CHECK REAR OXYGEN SENSOR.
Measure the resistance between connector
terminals of rear oxygen sensor.
Te r m i n a l s
No. 3 — No. 4
Is the resistance less than 1
Ω?
Replace the rear
oxygen sensor.
FU(H6DO)-30,
Rear Oxygen Sen-
sor.>
Te m p o r a r y p o o r
contact occurs.
Check poor con-
tact of connector.
Page 1350 of 2453

EN(H6DO)(diag)-189
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK ANY OTHER DTC ON DISPLAY.Is any other DTC displayed? Check DTC using
“List of Diagnostic
Tr o u b l e C o d e
(DTC)”.
EN(H6DO)(diag)-
69, List of Diag-
nostic Trouble
Code (DTC).>
NOTE:
In this case, it is
not necessary to
inspect DTC
P0137.
Go to step 2.
2CHECK REAR OXYGEN SENSOR DATA.
1) Warm-up the engine until engine coolant
temperature is above 70°C (158°F), and keep
the engine speed at 5,000 rpm.
2) Read the data of rear oxygen sensor signal
using Subaru Select Monitor or general scan
tool.
NOTE:•Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”.
to EN(H6DO)(diag)-26, Subaru Select Moni-
tor.>
•General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
Is the voltage more than 490
mV?
Go to step 6.Go to step 3.
3CHECK REAR OXYGEN SENSOR DATA.
1) Warm-up the engine until engine coolant
temperature is above 70°C (158°F), and keep
the engine speed at 5,000 rpm.
2) Read the data of rear oxygen sensor signal
using Subaru Select Monitor or general scan
tool.
NOTE:
•Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”.
to EN(H6DO)(diag)-26, Subaru Select Moni-
tor.>
•General scan tool
For detailed operation procedure, refer to the
general scan tool operation manual.
Is the voltage 250 mV or less? Go to step 6.Go to step 4.
4CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness
between ECM and rear oxygen sensor con-
nector.
Connector & terminal
(B135) No. 4 — (E61) No. 3:
(B135) No. 30 — (E61) No. 4:
Is the resistance more than
3Ω?
Repair the open
circuit of harness
between ECM and
rear oxygen sen-
sor connector.
Go to step 5.
Page 1351 of 2453

EN(H6DO)(diag)-190
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
5CHECK HARNESS BETWEEN REAR OXY-
GEN SENSOR AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from rear oxygen
sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between rear oxygen
sensor harness connector and chassis ground.
Connector & terminal
(E61) No. 3 (+) — Chassis ground (–):
Is the voltage 0.2 — 0.5 V? Replace the rear
oxygen sensor.
FU(H6DO)-30,
Rear Oxygen Sen-
sor.>
Repair the har-
ness and connec-
tor.
NOTE:In this case, repair
the following item:
•Open circuit
of harness be-
tween rear oxy-
gen sensor and
ECM connector
•Poor contact
in rear oxygen
sensor connec-
tor
•Poor contact
in ECM connec-
tor
6 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:Check the following item.
•Loose part and incomplete installation of ex-
haust system
•Damage (crack, hole etc.) of parts
•Looseness and ill fitting of parts between
front oxygen (A/F) sensor and rear oxygen sen-
sor
Is there any fault in exhaust
system?
Repair or replace
faulty par ts.
Replace the rear
oxygen sensor.
FU(H6DO)-30,
Rear Oxygen Sen-
sor.>
Step Check Yes No
Page 1354 of 2453
EN(H6DO)(diag)-193
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
front oxygen (A/F) sensor connector.
3) Measure the resistance of harness
between ECM and chassis ground.
Connector & terminal
(B135) No. 10 — Chassis ground:
(B135) No. 11 — Chassis ground:
Is the resistance more than 1
MΩ?
Replace the front
oxygen (A/F) sen-
sor.
FU(H6DO)-28,
Front Oxygen (A/
F) Sensor.>
Repair the ground
short circuit of har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.
Page 1357 of 2453
EN(H6DO)(diag)-196
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to ON.
2) Disconnect the connector from front oxygen
(A/F) sensor.
3) Measure the voltage of harness between
ECM connector and chassis ground.
Connector & terminal
(B135) No. 10 (+) — Chassis ground (–):
(B135) No. 11 (+) — Chassis ground (–):
Is the voltage more than 8 V? Replace the front
oxygen (A/F) sen-
sor.
FU(H6DO)-28,
Front Oxygen (A/
F) Sensor.>
Repair the battery
short circuit of har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.
Page 1360 of 2453
EN(H6DO)(diag)-199
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK ANY OTHER DTC ON DISPLAY.Is any other DTC displayed? Check DTC using
“List of Diagnostic
Tr o u b l e C o d e
(DTC)”.
EN(H6DO)(diag)-
69, List of Diag-
nostic Trouble
Code (DTC).>
NOTE:
In this case, it is
not necessary to
inspect DTC
P0133.
Go to step 2.
2 CHECK EXHAUST SYSTEM.
NOTE:Check the following item.
•Loose installation of front portion of exhaust
pipe onto cylinder heads
•Loose connection between front exhaust
pipe and front catalytic converter
•Damage of exhaust pipe resulting in a hole
Is there any fault in exhaust
system?
Repair the exhaust
system.
Replace the front
oxygen (A/F) sen-
sor.
FU(H6DO)-28,
Fr o nt Ox yg en ( A /
F) Sensor.>
Page 1363 of 2453

EN(H6DO)(diag)-202
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
front oxygen (A/F) sensor connector.
3) Measure the resistance of harness
between ECM and front oxygen (A/F) sensor
connector.
Connector & terminal
(B135) No. 10 — (E24) No. 4:
(B135) No. 11 — (E24) No. 3:
Is the resistance less than 1
Ω?
Go to step 2.Repair the har-
ness and connec-
tor.
NOTE:In this case, repair
the following item:
•Open circuit
of harness be-
tween ECM and
front oxygen (A/
F) sensor con-
nector
•Poor contact
in front oxygen
(A/F) sensor
connector
•Poor contact
in ECM connec-
tor
2CHECK POOR CONTACT.
Check poor contact of front oxygen (A/F) sen-
sor connector.
Is there poor contact in front
oxygen (A/F) sensor connec-
tor?
Repair the poor
contact in front
oxygen (A/F) sen-
sor connector.
Replace the front
oxygen (A/F) sen-
sor.
FU(H6DO)-28,
Fr o nt Ox yg en ( A /
F) Sensor.>