Subaru Legacy (2005 year). Service manual — part 325

EN(H4DOTC)(diag)-69

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

B: 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, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
37, OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOTC)(diag)-30, PROCE-
DURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-03522

SBF-5

B47

1

2

4

6

3

5

E

E

B21

F2

54

A6

A7

A2

A3

A26

A33

A25

ECM

B134

3

1

4

2

B18

3 4

1 2

3

4

1

2

5

6

B21

B47

B18

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

MAIN RELAY

FRONT OXYGEN
(A/F) SENSOR

BATTERY

A:

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:

EN(H4DOTC)(diag)-70

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK GROUND CIRCUIT FOR ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and chassis ground.

Connector & terminal

(B134) No. 6 — Chassis ground:
(B136) No. 7 — Chassis ground:

Is the resistance less than 5
Ω?

Go to step 2.

Repair the open
circuit of harness
between ECM
connector and
chassis ground.

2

CHECK VOLTAGE BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR.
Measure the voltage between ECM connector
and chassis ground.

Connector & terminal

(B137) No. 2 (+) — Chassis ground (

−

):

(B137) No. 3 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Repair the battery

short circuit of har-
ness between
ECM and front
oxygen (A/F) sen-
sor connector.

Repair the poor
contact in ECM
connector.

EN(H4DOTC)(diag)-71

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

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

DTC DETECTING CONDITION:
Detects when malfunction occurs in 2 continuous driving cycles.

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
37, OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOTC)(diag)-30, PROCE-
DURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-03555

1 2 3 4
5 6 7 8

B83

BATTERY

MAIN RELAY

B47

1

2

4

6

3

5

E

E

B21

E2

35

*

*

B83

3

4

1

2

5

6

B135

B47

B19

B136

1

4

2

3

T6

REAR
OXYGEN SENSOR

B4

B1

B2

D25

D31

C35

ECM

B136

B137

C:

B135

B:

D:

1

2

3

4

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

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

2 1
4 3

*

: TERMINAL No. RANDOM ARRANGEMENT

EN(H4DOTC)(diag)-72

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

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

(B135) No. 1 — Chassis ground:
(B135) No. 4 — Chassis ground:

Is the resistance less than 5
Ω?

Go to step 2.

Repair the har-
ness and connec-
tor.

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

2

CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR.
1) Disconnect the connector from rear oxygen
sensor.
2) Measure the resistance between ECM con-
nector and chassis ground.

Connector & terminal

(B135) No. 2 — Chassis ground:

Is the resistance more than 1
M

Ω?

Go to step 3.

Repair the ground
short circuit of har-
ness between
ECM and rear oxy-
gen sensor.

3

CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR.
Measure the resistance between ECM connec-
tor and chassis ground.

Connector & terminal

(B135) No. 2 — Chassis ground:

Does the resistance change by
shaking the ECM harness and
connector?

Repair the poor
contact in ECM
connector.

Go to step 4.

4

CHECK POWER SUPPLY TO REAR OXY-
GEN SENSOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.

Connector & terminal

(T6) No. 1 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Go to step 5.

Repair the power
supply line.

NOTE:
In this case, repair
the following:
• Open circuit of
harness between
main relay and
rear oxygen sen-
sor connector
• Poor contact in
rear oxygen sen-
sor connector
• Poor contact in
coupling connector