Subaru 2004 LEGACY User manual

FUJI HEAVY INDUSTRIES LTD. G2320GE4
2004 LEGACY SERVICE MANUAL QUICK REFERENCE INDEX
ENGINE SECTION 3
This service manual has been prepared
to provide SUBARU service personnel
with the necessary information and data
for the correct maintenance and repair
of SUBARU vehicles.
This manual includes the procedures
for maintenance, disassembling, reas-
sembling, inspection and adjustment of
components and diagnostics for guid-
ance of experienced mechanics.
Please peruse and utilize this manual
fully to ensure complete repair work for
satisfying our customers by keeping
their vehicle in optimum condition.
When replacement of parts during
repair work is needed, be sure to use
SUBARU genuine parts.
All information, illustration and specifi-
cations contained in this manual are
based on the latest product information
available at the time of publication
approval.
FUEL INJECTION (FUEL SYSTEMS) FU(H6DO)
EMISSION CONTROL
(AUX. EMISSION CONTROL DEVICES) EC(H6DO)
INTAKE (INDUCTION) IN(H6DO)
MECHANICAL ME(H6DO)
EXHAUST EX(H6DO)
COOLING CO(H6DO)
LUBRICATION LU(H6DO)
SPEED CONTROL SYSTEMS SP(H6DO)
IGNITION IG(H6DO)
STARTING/CHARGING SYSTEMS SC(H6DO)
ENGINE (DIAGNOSTICS) EN(H6DO)(diag)

ENGINE (DIAGNOSTICS)
EN(H6DO)(diag)
Page
1. Basic Diagnostic Procedure........................................................................2
2. Check List for Interview...............................................................................3
3. General Description ....................................................................................5
4. Electrical Component Location ...................................................................8
5. Engine Control Module (ECM) I/O Signal .................................................17
6. Engine Condition Data..............................................................................21
7. Data Link Connector .................................................................................22
8. OBD-II General Scan Tool........................................................................23
9. Subaru Select Monitor...............................................................................25
10. Read Diagnostic Trouble Code (DTC)......................................................32
11. Inspection Mode........................................................................................33
12. Drive Cycle................................................................................................38
13. Clear Memory Mode..................................................................................40
14. Compulsory Valve Operation Check Mode...............................................41
15. Malfunction Indicator Light........................................................................43
16. Diagnostics for Engine Starting Failure.....................................................52
17. List of Diagnostic Trouble Code (DTC).....................................................66
18. Diagnostic Procedure with Diagnostic Trouble Code (DTC).....................72
19. General Diagnostic Table........................................................................265

EN(H6DO)(diag)-72
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
18.Diagnostic Procedure with Diagnostic Trouble Code (DTC)
A: DTC P0011 “A” CAMSHAFT POSITION - TIMING OVER-ADVANCED OR SYS-
TEM PERFORMANCE (BANK 1)
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
TROUBLE SYMPTOM:
• Engine stalls.
• Erroneous idling
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-40,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-33, Inspection
Mode.>.
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)”. <Ref. to
EN(H6DO)(diag)-
66, List of Diag-
nostic Trouble
Code (DTC).>
Go to step 2.
2 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Measure the AVCS system operating angle
and oil flow control solenoid valve duty output
using Subaru Select Monitoror OBD-II general
scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to the
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. <Ref. to
EN(H6DO)(diag)-25, Subaru Select Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.
Is the AVCS system operating
angle approx. 0 deg., and oil
flow control solenoid valve duty
output approx. 10%?
Check the follow-
ing and repair or
replace if neces-
sary.
• Oil pipe (clog)
• Oil flow con-
trol solenoid
valve (clog or
dirt of oil rout-
ing, setting of
spring, clog of
valve)
• Intake cam-
shaft (dirt, dam-
age of
camshaft)
• Timing chain
(matching of
timing mark)
A temporary mal-
function.
Perform the follow-
ing, and clean the
oil routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replacetheoilfilter
and engine oil.

EN(H6DO)(diag)-73
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
B: DTC P0021 “A” CAMSHAFT POSITION - TIMING OVER-ADVANCED OR SYS-
TEM PERFORMANCE (BANK 2)
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
TROUBLE SYMPTOM:
• Engine stalls.
• Erroneous idling
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-40,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-33, Inspection
Mode.>.
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)”. <Ref. to
EN(H6DO)(diag)-
66, List of Diag-
nostic Trouble
Code (DTC).>
Go to step 2.
2 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Measure the AVCS system operating angle
and oil flow control solenoid valve duty output
using Subaru Select Monitoror OBD-II general
scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to the
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. <Ref. to
EN(H6DO)(diag)-25, Subaru Select Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.
Is the AVCS system operating
angle approx. 0 deg., and oil
flow control solenoid valve duty
output approx. 10%?
Check the follow-
ing and repair or
replace if neces-
sary.
• Engine oil
(amount, dirt)
• Oil pipe (clog)
• Oil flow con-
trol solenoid
valve (clog or
dirt of oil rout-
ing, setting of
spring, clog of
valve)
• Intake cam-
shaft (dirt, dam-
age of
camshaft)
• Timing chain
(matching of
timing mark)
A temporary mal-
function.
Perform the follow-
ing, and clean the
oil routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replacetheoilfilter
and engine oil.

EN(H6DO)(diag)-74
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
C: DTC P0030 HO2S HEATER CONTROL CIRCUIT (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-40,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-33, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:
BATTERY
SBF-6
B47
MAIN RELAY
1
2
3
5
4
6
A4 A5 A6 A7
2
52
54
B21
E2
ECM
A34 A27
B7 A1 A2 A3
A26 A33
4 1 3
FRONT
OXYGEN
(A/F)
SENSOR LH
E24
2
B135B:B134A:
4
3 1
FRONT
OXYGEN
(A/F)
SENSOR RH
E47
E3
B22
8
5 6
E3
B22
2 1 3 4
B47
34
5 6
12
A25
B22
1234
5678
9
10 11 12
13 14 15 16
34
12
E47 E24 B135
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B:B134
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429 3230 31
A: B21
1234
12 13 14 15
5678
16 17 18 19
9 10 11
20 21 22
23 24 25 26 27 28 29 30 31 32 33
3534 3736 3938 4140
4342 44 45 4746
4948 5150 5352 54
EE
EN-02495
B135B:B134A:
7

EN(H6DO)(diag)-75
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Start the engine, and warm-up the engine.
2) Turn the ignition switch to OFF.
3) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
4) Measure the resistance of harness
between ECM and front oxygen (A/F) sensor
connector.
Connector & terminal
(B134) No. 2 — (E47) No. 1:
(B134) No. 3 — (E47) No. 1:
Is the resistance less than 1
Ω?Go to step 2. Repair the open circuit in harness
between ECM and
front oxygen (A/F)
sensor connector.
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance of harness between
ECM and front oxygen (A/F) sensor connector.
Connector & terminal
(B134) No. 26 — (E47) No. 4:
(B134) No. 33 — (E47) No. 3:
Is the resistance less than 1
Ω?Go to step 3. Repair the open circuit in harness
between ECM and
front oxygen (A/F)
sensor connector.
3 CHECK HARNESS BETWEEN MAIN RELAY
AND FRONT OXYGEN (A/F) SENSOR CON-
NECTOR.
Measure the resistance of harness between
main relay and front oxygen (A/F) sensor con-
nector.
Connector & terminal
(B47) No. 3 — (E47) No. 2:
Is the resistance less than 1
Ω?Go to step 4. Repair the open circuit in harness
between main
relay and front
oxygen (A/F) sen-
sor connector.
4 CHECK FRONT OXYGEN (A/F) SENSOR.
Measure the resistance between front oxygen
(A/F) sensor connector terminals.
Terminals
No. 2 — No. 1:
Is the resistance less than 5
Ω?Go to step 5. Replace the front oxygen (A/F) sen-
sor. <Ref. to
FU(H6DO)-30,
Front Oxygen (A/
F) Sensor.>
5 CHECK POOR CONTACT.
Check poor contact in ECM and front oxygen
(A/F) sensor connector.
Is there poor contact inECM or
front oxygen (A/F) sensor con-
nector?
Repair the poor
contact in ECM or
front oxygen (A/F)
sensor connector.
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(H6DO)-30,
Front Oxygen (A/
F) Sensor.>

EN(H6DO)(diag)-76
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
D: DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-40,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-33, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:
BATTERY
SBF-6
B47
MAIN RELAY
1
2
3
5
4
6
A4 A5 A6 A7
2
52
54
B21
E2
ECM
A34 A27
B7 A1 A2 A3
A26 A33
4 1 3
FRONT
OXYGEN
(A/F)
SENSOR LH
E24
2
B135B:B134A:
4
3 1
FRONT
OXYGEN
(A/F)
SENSOR RH
E47
E3
B22
8
5 6
E3
B22
2 1 3 4
B47
34
5 6
12
A25
B22
1234
5678
9
10 11 12
13 14 15 16
34
12
E47 E24 B135
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B:B134
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429 3230 31
A: B21
1234
12 13 14 15
5678
16 17 18 19
9 10 11
20 21 22
23 24 25 26 27 28 29 30 31 32 33
3534 3736 3938 4140
4342 44 45 4746
4948 5150 5352 54
EE
EN-02495
B135B:B134A:
7

EN(H6DO)(diag)-77
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK POWER SUPPLY TO FRONT OXY-
GEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from front oxygen
(A/F) sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between front oxygen
(A/F) sensor connector and engine ground.
Connector & terminal
(E47) No. 2 (+) — Engine ground (
− ):
Is the voltage more than 10 V? Go to step 2. Repair the power
supply line.
NOTE:
In this case repair
the following:
• Open circuit in
harness between
main relay and
front oxygen (A/F)
sensor connector
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
main relay connec-
tor
2 CHECK GROUND CIRCUIT FOR ECM.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B134) No. 4 — Chassis ground:
(B134) No. 5 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B134) No. 7 — Chassis ground:
Is the resistance less than 5
Ω?Go to step 3. Repair the har- ness and connec-
tor.
NOTE:
In this case repair
the following:
• Open circuit in
harness between
ECM and engine
ground terminal
• Poor contact in
ECM connector
• Poor contact in
coupling connector
3 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of front oxygen (A/F) sensor
heater current using Subaru Select Monitor or
the OBD-II general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to the
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. <Ref. to
EN(H6DO)(diag)-25, Subaru Select Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.
Is the current more than 0.2 A? Repair the poor
contact in connec-
tor.
NOTE:
In this case repair
the following:
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
coupling connector
• Poor contact in
ECM connector
Go to step 4.
4 CHECK OUTPUT SIGNAL FROM ECM.
1) Start and idle the engine.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 2 (+) — Chassis ground (
− ):
(B134) No. 3 (+) — Chassis ground (
− ):
Is the voltage less than 1 V? Go to step 6. Go to step 5.
5 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B134) No. 2 (+) — Chassis ground (
− ):
(B134) No. 3 (+) — Chassis ground (
− ):
Does the voltage change by
shaking the ECM harness and
connector while monitoring the
value of voltage meter?
Repair the poor
contact in ECM
connector.
Go to step 6.

EN(H6DO)(diag)-78
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
6 CHECK FRONT OXYGEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between front oxy-
gen (A/F) sensor connector terminals.
Terminals
No. 2 — No. 1:
Is the resistance less than 10
Ω?Repair the har- ness and connec-
tor.
NOTE:
In this case repair
the following:
• Open or ground
short circuit in har-
nessbetweenfront
oxygen (A/F) sen-
sor and ECM con-
nector
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
ECM connector
• Poor contact in
coupling connector
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(H6DO)-30,
Front Oxygen (A/
F) Sensor.>
Step Check Yes No

EN(H6DO)(diag)-79
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
E: DTC P0032 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-40,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-33, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:
BATTERY
SBF-6
B47
MAIN RELAY
1
2
3
5
4
6
A4 A5 A6 A7
2
52
54
B21
E2
ECM
A34 A27
B7 A1 A2 A3
A26 A33
4 1 3
FRONT
OXYGEN
(A/F)
SENSOR LH
E24
2
B135B:B134A:
4
3 1
FRONT
OXYGEN
(A/F)
SENSOR RH
E47
E3
B22
8
5 6
E3
B22
2 1 3 4
B47
34
5 6
12
A25
B22
1234
5678
9
10 11 12
13 14 15 16
34
12
E47 E24 B135
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B:B134
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429 3230 31
A: B21
1234
12 13 14 15
5678
16 17 18 19
9 10 11
20 21 22
23 24 25 26 27 28 29 30 31 32 33
3534 3736 3938 4140
4342 44 45 4746
4948 5150 5352 54
EE
EN-02495
B135B:B134A:
7

EN(H6DO)(diag)-80
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK OUTPUT SIGNAL FROM ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 2 (+) — Chassis ground ( − ):
(B134) No. 3 (+) — Chassis ground (
− ):
Is the voltage more than 8 V? Go to step 2. Go to step 3.
2 CHECK FRONT OXYGEN (A/F) SENSOR
HEATER CURRENT.
1) Turn the ignition switch to OFF.
2) Repair the battery short circuit in harness
between ECM and front oxygen (A/F) sensor
connector.
3) Turn the ignition switch to ON.
4) Read the data of front oxygen (A/F) sensor
heater current using Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to the
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. <Ref. to EN(H6DO)(di-
ag)-25, Subaru Select Monitor.>
Is the current more than 2.3 A? Replace the ECM.
<Ref. to
FU(H6DO)-34,
Engine Control
Module (ECM).>
END.
3 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B134) No. 2 (+) — Chassis ground (
− ):
(B134) No. 3 (+) — Chassis ground (
− ):
Does the voltage change by
shaking the ECM harness and
connector?
Repair the battery
short circuit in har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.
END.

EN(H6DO)(diag)-81
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
F: DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-40,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-33, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:
BATTERY
SBF-6
B47
MAIN RELAY
1
2
3
5
4
6
A4 A5 A6 A7
2
52 54
B21
E2
ECM
B3
D31 D25 D24
B2
C35
4
3
1
REAR
OXYGEN
SENSOR LH
E25
2
4
3 1
REAR
OXYGEN
SENSOR RH
E61
E3B22
14
13 15
E3
B22
10 11 12
9
B83
4
5
8
B47
34
5 6
12
EN-02496
B21
1234
12 13 14 15
5678
16 17 18 19
9 10 11
20 21 22
23 24 25 26 27 28 29 30 31 32 33
3534 3736 3938 4140
4342 44 45 4746
4948 5150 5352 54
B135
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B:B134
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429 3230 31
A:
16
B134A:
B135B:
B136C:
B137D:
B22
1234
5678
9
10 11 12
13 14 15 16
B136
56
78
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16
17 18 19 20 21
33 34
29 32 30 31 35
C: B137
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
D:
1234
5 6 7 8
B83
34
12
E25 E61
EE

EN(H6DO)(diag)-82
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK POWER SUPPLY TO REAR OXY-
GEN SENSOR.
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 connector and chassis ground.
Connector & terminal
(E61) No. 2 (+) — Chassis ground (
− ):
Is the voltage more than 10 V? Go to step 2. Repair the power
supply line.
NOTE:
In this case repair
the following:
• Open circuit in
harness between
main relay and
rear oxygen sen-
sor connector
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
main relay connec-
tor
2 CHECK GROUND CIRCUIT FOR ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM connector and chassis ground.
Connector & terminal
(B134) No. 4 — Chassis ground:
(B134) No. 5 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B134) No. 7 — Chassis ground:
Is the resistance less than 5
Ω?Go to step 3. Repair the har- ness and connec-
tor.
NOTE:
In this case repair
the following:
• Open circuit in
harness between
ECM and engine
ground terminal
• Poor contact in
ECM connector
• Poor contact in
coupling connector
3 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of rear oxygen sensor heater
current using Subaru Select Monitor or the
OBD-II general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to the
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. <Ref. to
EN(H6DO)(diag)-25, Subaru Select Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.
Is the current more than 0.2 A? Repair the con-
nector.
NOTE:
In this case repair
the following:
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
coupling connector
• Poor contact in
ECM connector
Go to step 4.
4 CHECK OUTPUT SIGNAL FROM ECM.
1) Start and idle the engine.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 2 (+) — Chassis ground (
− ):
Is the voltage less than 1 V? Go to step 7. Go to step 5.
5 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B135) No. 2 (+) — Chassis ground (
− ):
Does the voltage change by
shaking the ECM harness and
connector while monitoring the
value of voltage meter?
Repair the poor
contact in ECM
connector.
Go to step 6.

EN(H6DO)(diag)-83
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
6 CHECK OUTPUT SIGNAL FROM ECM.
1) Disconnect the connector from rear oxygen
sensor.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 2 (+) — Chassis ground (
− ):
Is the voltage less than 1 V? Replace the ECM.
<Ref. to
FU(H6DO)-34,
Engine Control
Module (ECM).>
Repair the battery
short circuit in har-
ness between
ECM and rear oxy-
gen sensor con-
nector. After
repair, replace the
ECM. <Ref. to
FU(H6DO)-34,
Engine Control
Module (ECM).>
7 CHECK REAR OXYGEN SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between rear oxy-
gen sensor connector terminals.
Terminals
No. 1 — No. 2:
Is the resistance less than 30
Ω?Repair the har- ness and connec-
tor.
NOTE:
In this case repair
the following:
• Open circuit in
harness between
rear oxygen sen-
sor and ECM con-
nector
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
ECM connector
• Poor contact in
coupling connector
Replace the rear
oxygen sensor.
<Ref. to
FU(H6DO)-32,
Rear Oxygen Sen-
sor.>
Step Check Yes No

EN(H6DO)(diag)-84
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
G: DTC P0038 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-40,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-33, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:
BATTERY
SBF-6
B47
MAIN RELAY
1
2
3
5
4
6
A4 A5 A6 A7
2
52 54
B21
E2
ECM
B3
D31 D25 D24
B2
C35
4
3
1
REAR
OXYGEN
SENSOR LH
E25
2
4
3 1
REAR
OXYGEN
SENSOR RH
E61
E3B22
14
13 15
E3
B22
10 11 12
9
B83
4
5
8
B47
34
5 6
12
EN-02496
B21
1234
12 13 14 15
5678
16 17 18 19
9 10 11
20 21 22
23 24 25 26 27 28 29 30 31 32 33
3534 3736 3938 4140
4342 44 45 4746
4948 5150 5352 54
B135
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B:B134
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429 3230 31
A:
16
B134A:
B135B:
B136C:
B137D:
B22
1234
5678
9
10 11 12
13 14 15 16
B136
56
78
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16
17 18 19 20 21
33 34
29 32 30 31 35
C: B137
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
D:
1234
5 6 7 8
B83
34
12
E25 E61
EE

EN(H6DO)(diag)-85
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK INPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B135) No. 2 (+) — Chassis ground (
− ):
Is the voltage more than 8 V? Go to step 2. Go to step 3.
2 CHECK CURRENT DATA.
1) Turn the ignition switch to OFF.
2) Repair the battery short circuit in harness
between ECM and rear oxygen sensor con-
nector.
3) Turn the ignition switch to ON.
4) Read the data of rear oxygen sensor heater
current using Subaru Select Monitor or the
OBD-II general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to the
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. <Ref. to
EN(H6DO)(diag)-25, Subaru Select Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.
Is the current more than 7 A? Replace the ECM.
<Ref. to
FU(H6DO)-34,
Engine Control
Module (ECM).>
END.
3 CHECK POOR CONTACT.
Check poor contact in ECM connector. Is the poor contact in ECM connector? Repair the poor contact in ECM
connector.
END.

EN(H6DO)(diag)-86
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
H: DTC P0050 HO2S HEATER CONTROL CIRCUIT (BANK 2 SENSOR 1)
DTC DETECTING CONDITION:
Two consecutive driving cycles with fault
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-40,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-33, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:
BATTERY
SBF-6
B47
MAIN RELAY
1
2
3
5
4
6
A4 A5 A6 A7
2
52
54
B21
E2
ECM
A34 A27
B7 A1 A2 A3
A26 A33
4 1 3
FRONT
OXYGEN
(A/F)
SENSOR LH
E24
2
B135B:B134A:
4
3 1
FRONT
OXYGEN
(A/F)
SENSOR RH
E47
E3
B22
8
5 6
E3
B22
2 1 3 4
B47
34
5 6
12
A25
B22
1234
5678
9
10 11 12
13 14 15 16
34
12
E47 E24 B135
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B:B134
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429 3230 31
A: B21
1234
12 13 14 15
5678
16 17 18 19
9 10 11
20 21 22
23 24 25 26 27 28 29 30 31 32 33
3534 3736 3938 4140
4342 44 45 4746
4948 5150 5352 54
EE
EN-02495
B135B:B134A:
7

EN(H6DO)(diag)-87
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Start the engine, and warm-up the engine.
2) Turn the ignition switch to OFF.
3) Disconnect the connector from ECM and
front oxygen (A/F) sensor.
4) Measure the resistance of harness
between ECM and front oxygen (A/F) sensor
connector.
Connector & terminal
(B134) No. 1 — (E24) No. 1:
(B135) No. 7 — (E24) No. 1:
Is the resistance less than 1
Ω?Go to step 2. Repair the open circuit in harness
between ECM and
front oxygen (A/F)
sensor connector.
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance of harness between
ECM and front oxygen (A/F) sensor connector.
Connector & terminal
(B134) No. 27 — (E24) No. 4:
(B134) No. 34 — (E24) No. 3:
Is the resistance less than 1
Ω?Go to step 3. Repair the open circuit in harness
between ECM and
front oxygen (A/F)
sensor connector.
3 CHECK HARNESS BETWEEN MAIN RELAY
AND FRONT OXYGEN (A/F) SENSOR CON-
NECTOR.
Measure the resistance of harness between
main relay and front oxygen (A/F) sensor con-
nector.
Connector & terminal
(B47) No. 3 — (E24) No. 2:
Is the resistance less than 1
Ω?Go to step 4. Repair the open circuit in harness
between main
relay and front
oxygen (A/F) sen-
sor connector.
4 CHECK FRONT OXYGEN (A/F) SENSOR.
Measure the resistance between front oxygen
(A/F) sensor connector terminals.
Terminals
No. 2 — No. 1:
Is the resistance less than 5
Ω?Go to step 5. Replace the front oxygen (A/F) sen-
sor. <Ref. to
FU(H6DO)-30,
Front Oxygen (A/
F) Sensor.>
5 CHECK POOR CONTACT.
Check poor contact in ECM and front oxygen
(A/F) sensor connector.
Is there poor contact inECM or
front oxygen (A/F) sensor con-
nector?
Repair the poor
contact in ECM or
front oxygen (A/F)
sensor connector.
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(H6DO)-30,
Front Oxygen (A/
F) Sensor.>

EN(H6DO)(diag)-88
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
I: DTC P0051 HO2S HEATER CONTROL CIRCUIT LOW (BANK 2 SENSOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-40,
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-33, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:
BATTERY
SBF-6
B47
MAIN RELAY
1
2
3
5
4
6
A4 A5 A6 A7
2
52
54
B21
E2
ECM
A34 A27
B7 A1 A2 A3
A26 A33
4 1 3
FRONT
OXYGEN
(A/F)
SENSOR LH
E24
2
B135B:B134A:
4
3 1
FRONT
OXYGEN
(A/F)
SENSOR RH
E47
E3
B22
8
5 6
E3
B22
2 1 3 4
B47
34
5 6
12
A25
B22
1234
5678
9
10 11 12
13 14 15 16
34
12
E47 E24 B135
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B:B134
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429 3230 31
A: B21
1234
12 13 14 15
5678
16 17 18 19
9 10 11
20 21 22
23 24 25 26 27 28 29 30 31 32 33
3534 3736 3938 4140
4342 44 45 4746
4948 5150 5352 54
EE
EN-02495
B135B:B134A:
7

EN(H6DO)(diag)-89
ENGINE (DIAGNOSTICS)
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
Step Check Yes No
1 CHECK POWER SUPPLY TO FRONT OXY-
GEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from front oxygen
(A/F) sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between front oxygen
(A/F) sensor connector and engine ground.
Connector & terminal
(E24) No. 2 (+) — Engine ground (
− ):
Is the voltage more than 10 V? Go to step 2. Repair the power
supply line.
NOTE:
In this case repair
the following:
• Open circuit in
harness between
main relay and
front oxygen (A/F)
sensor connector
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
main relay connec-
tor
2 CHECK GROUND CIRCUIT FOR ECM.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B134) No. 4 — Chassis ground:
(B134) No. 5 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B134) No. 7 — Chassis ground:
Is the resistance less than 5
Ω?Go to step 3. Repair the har- ness and connec-
tor.
NOTE:
In this case repair
the following:
• Open circuit in
harness between
ECM and engine
ground terminal
• Poor contact in
ECM connector
• Poor contact in
coupling connector
3 CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of front oxygen (A/F) sensor
heater current using Subaru Select Monitor or
the OBD-II general scan tool.
NOTE:
• Subaru Select Monitor
For detailed operation procedures, refer to the
“READ CURRENT DATA SHOWN ON DIS-
PLAY FOR ENGINE”. <Ref. to
EN(H6DO)(diag)-25, Subaru Select Monitor.>
• OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Operation Manual.
Is the current more than 0.2 A? Repair the poor
contact connector.
NOTE:
In this case repair
the following:
• Poor contact in
front oxygen (A/F)
sensor connector
• Poor contact in
coupling connector
• Poor contact in
ECM connector
Go to step 4.
4 CHECK OUTPUT SIGNAL FROM ECM.
1) Start and idle the engine.
2) Measure the voltage between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 1 (+) — Chassis ground (
− ):
(B135) No. 7 (+) — Chassis ground (
− ):
Is the voltage less than 1 V? Go to step 6. Go to step 5.
5 CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B134) No. 1 (+) — Chassis ground (
− ):
(B135) No. 7 (+) — Chassis ground (
− ):
Does the voltage change by
shaking the ECM harness and
connector while monitoring the
value of voltage meter?
Repair the poor
contact in ECM
connector.
Go to step 6.