Subaru Legacy IV (2008 year). Manual - part 122

 

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Subaru Legacy IV (2008 year). Manual - part 122

 

 

EN(H4SO)(diag)-91

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

C: DTC P0030 HO2S HEATER CONTROL CIRCUIT (BANK 1 SENSOR 1)

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-11, DTC P0030 HO2S HEATER CONTROL CIRCUIT
(BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-06835

B137

8

5

6

10 11 12 13 14 15

7

2

1

3

4

16

30

19 20

22
28 29

9

17

18

25

21

23

24

31

26 27

3

4

1

2

5

6

B327

SBF-5

E

E

E

B327

E22

6

4

5

3

2
1

6

4

1

3

B1

B9

B8

C3

C2

A5

D7

D1

D2

D3

36

52

34

35

37

B134

A:

B135

B:

B136

C:

B137

D:

B21

E2

ECM

B21

E2

50

51

3

4

E2

B21

E

E22

B138

B134

B135

A:

B:

B136

C:

D:

5

6

7

8

2

1

9

4

3

10

24

22 23

25

11 12 13 14 15

26 27

28

16 17

18 19 20 21

33 34

29

32

30 31

BATTERY

FRONT OXYGEN 

(A/F) SENSOR

A/F, OXYGEN 
SENSOR RELAY

B138

*

*

 : TERMINAL No. OPTIONAL  
 ARRANGEMENT

*

3

1

6 5 4

2

5

6

7

2

1

3

4

29

10 11 12 13 14 15

25

24

16

30

9

8

17 18 19

20
28

21 22 23

32

31

26 27

33

34 35

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

3 4

5 6

1 2

7 8

B21

1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33

34

35

42

43

36

37

38

39

48

49

50

51

52

53

54

40

41

44

45

46

47

EN(H4SO)(diag)-92

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND 
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Start and warm up 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

(B136) No. 2 — (E22) No. 4:
(B136) No. 3 — (E22) No. 4:

Is the resistance less than 1 

:? Go to step 2.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and front oxy-
gen (A/F) sensor
connector
• Poor contact of
coupling 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

(B135) No. 9 — (E22) No. 1:
(B135) No. 8 — (E22) No. 3:

Is the resistance less than 1 

:? Go to step 3.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and front oxy-
gen (A/F) sensor
connector
• Poor contact of
coupling connector

3

CHECK FRONT OXYGEN (A/F) SENSOR.
Measure the resistance between front oxygen 
(A/F) sensor connector terminals.

Terminals

No. 6 — No. 4:

Is the resistance between 2 — 
3

:?

Go to step 4.

Replace the front 
oxygen (A/F) sen-
sor. <Ref. to 
FU(H4SO)-35,
Front Oxygen (A/F) 
Sensor.>

4

CHECK POOR CONTACT.
Check for poor contact of ECM and front oxygen 
(A/F) sensor connector.

Is there poor contact in ECM 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(H4SO)-35,
Front Oxygen (A/F) 
Sensor.>

EN(H4SO)(diag)-93

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

D: DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 1)

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-13, DTC P0031 HO2S HEATER CONTROL CIRCUIT
LOW (BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-06835

B137

8

5

6

10 11 12 13 14 15

7

2

1

3

4

16

30

19 20

22
28 29

9

17

18

25

21

23

24

31

26 27

3

4

1

2

5

6

B327

SBF-5

E

E

E

B327

E22

6

4

5

3

2
1

6

4

1

3

B1

B9

B8

C3

C2

A5

D7

D1

D2

D3

36

52

34

35

37

B134

A:

B135

B:

B136

C:

B137

D:

B21

E2

ECM

B21

E2

50

51

3

4

E2

B21

E

E22

B138

B134

B135

A:

B:

B136

C:

D:

5

6

7

8

2

1

9

4

3

10

24

22 23

25

11 12 13 14 15

26 27

28

16 17

18 19 20 21

33 34

29

32

30 31

BATTERY

FRONT OXYGEN 

(A/F) SENSOR

A/F, OXYGEN 
SENSOR RELAY

B138

*

*

 : TERMINAL No. OPTIONAL  
 ARRANGEMENT

*

3

1

6 5 4

2

5

6

7

2

1

3

4

29

10 11 12 13 14 15

25

24

16

30

9

8

17 18 19

20
28

21 22 23

32

31

26 27

33

34 35

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

3 4

5 6

1 2

7 8

B21

1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33

34

35

42

43

36

37

38

39

48

49

50

51

52

53

54

40

41

44

45

46

47

EN(H4SO)(diag)-94

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

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

(E22) No. 6 (+) — Engine ground (–):

Is the voltage 10 V or more?

Go to step 2.

Repair the power 
supply line. Or 
replace the main 
relay.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
A/F, oxygen sen-
sor relay connector
and front oxygen
(A/F) sensor con-
nector
• Poor contact of
A/F, oxygen sen-
sor relay connector
• Poor contact of
coupling connector
• Malfunction of A/
F, oxygen sensor
relay

2

CHECK HARNESS BETWEEN ECM AND 
FRONT OXYGEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM.
3) Measure the resistance between ECM and 
front oxygen (A/F) sensor connector.

Connector & terminal

(B136) No. 2 — (E22) No. 4:
(B136) No. 3 — (E22) No. 4:

Is the resistance less than 1 

:? Go to step 3.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and front oxy-
gen (A/F) sensor
connector
• Poor contact of
coupling connector

3

CHECK GROUND CIRCUIT FOR ECM.
Measure the resistance of harness between 
ECM and chassis ground.

Connector & terminal

(B134) No. 5 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 2 — Chassis ground:
(B137) No. 3 — Chassis ground:
(B137) No. 7 — Chassis ground:

Is the resistance less than 5 

:? Go to step 4.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
ECM and engine
ground
• Poor contact in
ECM connector
• Poor contact of
coupling connector

4

CHECK FRONT OXYGEN (A/F) SENSOR.
Measure the resistance between front oxygen 
(A/F) sensor connector terminals.

Terminals

No. 6 — No. 4:

Is the resistance between 2 — 
3

:?

Repair the poor 
contact of ECM 
connector.

Replace the front 
oxygen (A/F) sen-
sor. <Ref. to 
FU(H4SO)-35,
Front Oxygen (A/F) 
Sensor.>

 

 

 

 

 

 

 

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