Subaru Legacy IV (2008 year). Manual - part 576

EN(H6DO)(diag)-277

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DD:DTC P1154 O2 SENSOR CIRCUIT RANGE/PERFORMANCE (LOW) (BANK 2 

SENSOR 1)

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H6DO)-166, DTC P1154 O2 SENSOR CIRCUIT RANGE/PER-
FORMANCE (LOW) (BANK 2 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H6DO)(diag)-52,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H6DO)(diag)-44, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

SBF-5

BATTERY

E

E3

B22

B47

1

2

3

5

4

6

MAIN RELAY

E3

B22

8

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

*

3

4

5

6

1

2

B47

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

B22

3 4

1 2

E47

E24

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:

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

B137

D:

1 2 3 4
5 6 7 8

B138

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

B135

B:

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

B134

A:

B11

2

E24

FRONT 

OXYGEN (A/F) 

SENSOR LH

3

4

B10

1

B7

B6

C2

C3

B8

4

1

3

B9

ECM

B135

B:

B134

A:

B137

D:

B136

C:

D3

A3

D2

D1

D7

A5

35

34

52

36

37

B21

E2

E

E

EN-06867

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

2

E47

FRONT 

OXYGEN (A/F) 

SENSOR RH

5

6

7

4

2

1

3

B138

*

*

B1

EN(H6DO)(diag)-278

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK FRONT OXYGEN (A/F) SENSOR 
CONNECTOR AND COUPLING CONNEC-
TOR.

Has water entered the connec-
tor?

Completely 
remove any water 
inside.

Go to step 2.

2

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

Connector & terminal

(B135) No. 11 — (E24) No. 3:
(B135) No. 10 — (E24) 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 POOR CONTACT.
Check for poor contact in the front oxygen (A/F) 
sensor connector.

Is there poor contact in front 
oxygen (A/F) sensor connec-
tor?

Repair the poor 
contact of the front 
oxygen (A/F) sen-
sor connector.

Replace the front 
oxygen (A/F) sen-
sor. <Ref. to 
FU(H6DO)-32, 
Front Oxygen (A/F) 
Sensor.>

EN(H6DO)(diag)-279

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DE:DTC P1155 O2 SENSOR CIRCUIT RANGE/PERFORMANCE (HIGH) (BANK 2 

SENSOR 1)

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H6DO)-166, DTC P1155 O2 SENSOR CIRCUIT RANGE/PER-
FORMANCE (HIGH) (BANK 2 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H6DO)(diag)-52,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H6DO)(diag)-44, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

SBF-5

BATTERY

E

E3

B22

B47

1

2

3

5

4

6

MAIN RELAY

E3

B22

8

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

*

3

4

5

6

1

2

B47

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

B22

3 4

1 2

E47

E24

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:

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

B137

D:

1 2 3 4
5 6 7 8

B138

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

B135

B:

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

B134

A:

B11

2

E24

FRONT 

OXYGEN (A/F) 

SENSOR LH

3

4

B10

1

B7

B6

C2

C3

B8

4

1

3

B9

ECM

B135

B:

B134

A:

B137

D:

B136

C:

D3

A3

D2

D1

D7

A5

35

34

52

36

37

B21

E2

E

E

EN-06867

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

2

E47

FRONT 

OXYGEN (A/F) 

SENSOR RH

5

6

7

4

2

1

3

B138

*

*

B1

EN(H6DO)(diag)-280

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DF:DTC P1160 RETURN SPRING FAILURE

NOTE:
For the diagnostic procedure, refer to DTC P2101. <Ref. to EN(H6DO)(diag)-324, DTC P2101 THROTTLE
ACTUATOR CONTROL MOTOR CIRCUIT RANGE/PERFORMANCE, Diagnostic Procedure with Diagnos-
tic Trouble Code (DTC).>

Step

Check

Yes

No

1

CHECK FRONT OXYGEN (A/F) SENSOR 
CONNECTOR AND COUPLING CONNEC-
TOR.

Has water entered the connec-
tor?

Completely 
remove any water 
inside.

Go to step 2.

2

CHECK HARNESS BETWEEN ECM AND 
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM.
3) Measure the resistance between ECM and 
chassis ground.

Connector & terminal

(B135) No. 11 — Chassis ground:
(B135) No. 10 — Chassis ground:

Is the resistance 1 M

: or 

more?

Go to step 3.

Repair the ground 
short circuit of har-
ness between 
ECM and front oxy-
gen (A/F) sensor 
connector.

3

CHECK OUTPUT SIGNAL FOR ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM and 
chassis ground.

Connector & terminal

(B135) No. 11 (+) — Chassis ground (–):

Is the voltage 4.5 V or more?

Go to step 5.

Go to step 4.

4

CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between ECM and chassis 
ground.

Connector & terminal

(B135) No. 10 (+) — Chassis ground (–):

Is the voltage 4.95 V or more?

Go to step 5.

Replace the front 
oxygen (A/F) sen-
sor. <Ref. to 
FU(H6DO)-32, 
Front Oxygen (A/F) 
Sensor.>

5

CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between ECM and chassis 
ground.

Connector & terminal

(B135) No. 11 (+) — Chassis ground (–):
(B135) No. 10 (+) — Chassis ground (–):

Is the voltage 8 V or more?

Repair the short 
circuit to power in 
the harness 
between ECM and 
front oxygen (A/F) 
sensor connector. 
After repair, 
replace the ECM. 
<Ref. to 
FU(H6DO)-38,
Engine Control 
Module (ECM).>

Repair the poor 
contact of ECM 
connector.