Subaru Legacy (2005 year). Manual - part 208

EN(H4SO 2.5)(diag)-117

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK OPTION CODE.

Is the option code EC, EK, EH, 
ER or K4?

Go to step 2.

Refer to EN(H4SO 
2.0) section. <Ref. 
to EN(H4SO 
2.0)(diag)-64, List 
of Diagnostic Trou-
ble Code (DTC).>

NOTE:
Fuel injection sys-
tem for KA and KS
model is the same
as 2.0 L model.

2

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(H4SO 
2.5)(diag)-69, List 
of Diagnostic Trou-
ble Code (DTC).>

NOTE:
In this case, it is
not necessary to
inspect DTC
P0125.

Go to step 3.

3

CHECK ENGINE COOLING SYSTEM.

NOTE:

Check the following items.
• Thermostat open stuck
• Engine coolant level
• Coolant freeze
• Tire diameter

Is there any fault in engine 
cooling system?

Replace the ther-
mostat. <Ref. to 
CO(H4SO 2.0)-18, 
Thermostat.>

Replace the 
engine coolant 
temperature sen-
sor. <Ref. to 
FU(H4SO 2.5)-20, 
Engine Coolant 
Temperature Sen-
sor.>

EN(H4SO 2.5)(diag)-118

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Q: DTC P0131 O2 SENSOR CIRCUIT LOW VOLTAGE (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(H4SO 2.5)(diag)-
40, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO 2.5)(diag)-33, Inspection Mode.>.
WIRING DIAGRAM:
• EC, EK, EH, ER and K4 model

• KA and KS model

NOTE:
Fuel injection system for KA and KS model is the same as 2.0 L model. Refer to EN(H4SO 2.0) section.

EN-03457

3

4

1

2

5

6

B327

SBF-5

E

E

B327

E24

6
4

5
3

2
1

25

33

26

3

2

6

7

52

B134

B21

E2

B21

E2

50

51

3

4

E2

B21

E

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

E24

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

ECM

BATTERY

FRONT OXYGEN

(A/F) SENSOR

OXYGEN (A/F) 
SENSOR RELAY

1

3

4 5 6

2

3

4

1

6

EN(H4SO 2.5)(diag)-119

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK OPTION CODE.

Is the option code EC, EK, EH, 
ER or K4?

Go to step 2.

Refer to EN(H4SO 
2.0) section. <Ref. 
to EN(H4SO 
2.0)(diag)-64, List 
of Diagnostic Trou-
ble Code (DTC).>

NOTE:
Fuel injection sys-
tem for KA and KS
model is the same
as 2.0 L model.

2

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

Connector & terminal

(B134) No. 26 — Chassis ground:
(B134) No. 33 — Chassis ground:

Is the resistance more than 1 
M

Ω?

Replace the front 
oxygen (A/F) sen-
sor. <Ref. to 
FU(H4SO 2.5)-35, 
Front Oxygen (A/
F) Sensor.>

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

EN(H4SO 2.5)(diag)-120

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

R: DTC P0132 O2 SENSOR CIRCUIT HIGH VOLTAGE (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(H4SO 2.5)(diag)-
40, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO 2.5)(diag)-33, Inspection Mode.>.
WIRING DIAGRAM:
• EC, EK, EH, ER and K4 model

• KA and KS model

NOTE:
Fuel injection system for KA and KS model is the same as 2.0 L model. Refer to EN(H4SO 2.0) section.

EN-03457

3

4

1

2

5

6

B327

SBF-5

E

E

B327

E24

6
4

5
3

2
1

25

33

26

3

2

6

7

52

B134

B21

E2

B21

E2

50

51

3

4

E2

B21

E

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

E24

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

ECM

BATTERY

FRONT OXYGEN

(A/F) SENSOR

OXYGEN (A/F) 
SENSOR RELAY

1

3

4 5 6

2

3

4

1

6