Subaru Legacy IV (2008 year). Manual - part 319

EN(H4DOTC)(diag)-97

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

G: DTC P0032 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 1)

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-18, DTC P0032 HO2S HEATER CONTROL CIRCUIT
HIGH (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(H4DOTC)(diag)-
52, OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-43, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-05669

SBF-5

B47

B21

E2

B21

E2

1

2

4

6

3

5

E

E

C2

C3

B8

B9

B1

B134

4

3

2

1

E79

3 4

1 2

3

4

1

2

5

6

B21

B47

E79

B134

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

A:

B135

B:

B136

C:

B137

D:

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

A:

D2

A5

D3

E2

B21

E

35

34

40

D7

36

D1

37

B138

*

*

*

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

B136

C:

B135

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

29 30 31

32 33

34 35

B137

5

6

7

8

2

1

9

4

3

10

22 23

11 12 13 14 15

24 25

26

16 17

18 19 20 21

27

28 29

30 31

B:

D:

1 2 3 4
5 6 7 8

B138

42

26

43

15

MAIN RELAY

BATTERY

FRONT 
OXYGEN (A/F)  
SENSOR

ECM

: TERMINAL No. OPTIONAL 
  ARRANGEMENT 
  AMONG 1, 2, 5  AND 6

EN(H4DOTC)(diag)-98

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND 
FRONT OXYGEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the voltage between ECM and 
chassis ground.

Connector & terminal

(B136) No. 3 (+) — Chassis ground (–):
(B136) No. 2 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Repair the short 
circuit to power in 
the harness 
between ECM and 
front oxygen (A/F) 
sensor connector.

Go to step 2.

2

CHECK GROUND CIRCUIT FOR ECM.
1) Disconnect the connectors from ECM.
2) Measure the resistance 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 

:? Repair the poor 

contact of ECM 
connector.

Repair the harness 
and connector.

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

EN(H4DOTC)(diag)-99

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

H: DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-20, DTC P0037 HO2S HEATER CONTROL CIRCUIT
LOW (BANK 1 SENSOR 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
52, OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-43, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-05670

B83

1 2 3 4
5 6 7 8

B138

B47

1

2

4

6

3

5

E

*

*

B138

B83

3

4

1

2

5

6

B135

B47

B19

B136

B:

C:

B137

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

35

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

29 30 31

32 33

34 35

5

6

7

8

2

1

9

4

3

10

22 23

11 12 13 14 15

24 25

26

16 17

18 19 20 21

27

28 29

30 31

B19

T5

2

2

T5

B19

3

1

4

B21

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

T6

SBF-5

*

1

*

2

1
1

*

*

2
2

C4

B4

B30

B1

B134

T6

B134

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

A:

B135

B:

B136

C:

B137

D:

A:

D2

A5

D3

E2

B21

E

35

34

40

D7

36

D1

37

1 2
3 4

3

1

4

MAIN RELAY

REAR
OXYGEN SENSOR

BATTERY

ECM

: TERMINAL No. OPTIONAL 
  ARRANGEMENT

: TERMINAL No. OPTIONAL 
  ARRANGEMENT 
  AMONG 1, 2, 5  AND 6

EN(H4DOTC)(diag)-100

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

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 engine ground.

Connector & terminal

(T6) No. 2 (+) — Engine ground (–):

Is the voltage 10 V or more?

Go to step 2.

Repair the power 
supply line.

NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
main relay and rear
oxygen sensor
• Poor contact of
main relay connec-
tor
• Poor contact of
coupling connector
• Malfunction of
main relay

2

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

Connector & terminal

(B136) No. 4 — (T6) No. 1:

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 of
harness between
the ECM and rear
oxygen sensor
• 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 REAR OXYGEN SENSOR.
Measure the resistance between rear oxygen 
sensor connector terminals.

Terminals

No. 1 — No. 2:

Is the resistance between 5 — 
7

:?

Repair the poor 
contact of ECM 
connector.

Replace the rear 
oxygen sensor. 
<Ref. to 
FU(H4DOTC)-48, 
Rear Oxygen Sen-
sor.>