Subaru Legacy (2005 year). Manual - part 332

EN(H4DOTC)(diag)-97

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

N: DTC P0123 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT 

HIGH

DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
• Erroneous idling
• Engine stalls.
• Poor driving performance
WIRING DIAGRAM:

EN-03524

SBF-7

B135

B:

B137

B136

D:

B362

B84

B138

B122

E1

B20

E57

C:

B135

B362

B20

B21

E57

B84

B122

B138

B137

B136

E

E

D6

B35

16

15

*

*

*

*

7
3

E2

B21

39

38

19

20

35

36

37

4

6

1

2

3

5

D4

D5

C35

C16

B1

B4

D1

D2

D3

C29

C18

5

8

7

6

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

1 2

7 8

3
4

5
6

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

34 35

36 37 38 39 40 41

48 49

50 51 52 53 54

42 43

44 45

46 47

26 27 28 29 30 31 32 33

1 2 3 4
5 6 7 8

1 2 3 4 5 6

1

2

7

8 9

5

6

3

4

10 11 12

19 20 21

29

30 31

13 14 15 16 17

27

28

18

22 23

24 25

26

1

2

7

8 9

5

6

3

4

10 11 12

19

20 21

29 30 31

13 14 15 16 17

27

28

18

22 23

24 25

26

32 33

34 35

1

2

8 9

5

6

3

4

10 11 12

19 20 21

29 30

31

13 14 15 16

17

27

28

18

22 23 24 25 26

7

32 33 34 35

B:

D:

C:

ECM

BATTERY

MAIN RELAY

ELECTRONIC
THROTTLE 
CONTROL RELAY

ELECTRONIC
THROTTLE 
CONTROL

*

: TERMINAL No. RANDOM ARRANGEMENT

EN(H4DOTC)(diag)-98

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) Read the data of main throttle sensor signal 
using Subaru Select Monitor.

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to 
“READ CURRENT DATA FOR ENGINE”. <Ref. 
to EN(H4DOTC)(diag)-24, Subaru Select Mon-
itor.>

Is the voltage less than 4.63 
V?

Go to step 2.

Go to step 3.

2

CHECK POOR CONTACT.
Check poor contact in connector between 
ECM and electronic throttle control.

Is there poor contact in con-
nector between ECM and elec-
tronic throttle control?

Repair the poor 
contact.

Temporary poor 
contact occurred, 
but it is normal at 
present.

3

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Disconnect the connectors from electronic 
throttle control.
4) Measure the resistance between ECM con-
nector and electronic throttle control connector.

Connector & terminal

(B136) No. 18 — (E57) No. 6:
(B136) No. 35 — (E57) No. 3:

Is the resistance less than 1 
Ω?

Go to step 4.

Repair the open 
circuit of harness 
connector.

4

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to ON.
2) Measure the voltage between electronic 
throttle control connector and engine ground.

Connector & terminal

(E57) No. 6 (+) — Engine ground (

−

):

3) Check the voltage change by shaking the 
harness and connector of ECM, and engine 
harness connector, while monitoring the value 
with voltage meter.

Is the voltage less than 10 V?

Go to step 5.

Repair the battery 
short circuit of har-
ness between 
ECM connector 
and electronic 
throttle control 
connector.

5

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.

Connector & terminal

(B136) No. 18 — (B136) No. 16:

Is the resistance more than 1 
M

Ω?

Repair the poor 
contact in harness. 
Replace the elec-
tronic throttle con-
trol.

Repair the short 
circuit to sensor 
power supply.

EN(H4DOTC)(diag)-99

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

O: 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, 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)-100

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

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 connector and chassis ground.

Connector & terminal

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

Is the resistance more than 1 
M

Ω?

Go to step 2.

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

2

CHECK HARNESS BETWEEN ECM AND 
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance of harness between 
ECM connectors.

Connector & terminal

(B134) No. 26 — (B134) No. 33:

Is the resistance more than 1 
M

Ω?

Replace the front 
oxygen (A/F) sen-
sor. <Ref. to 
FU(H4DOTC)-32, 
Front Oxygen (A/
F) Sensor.>

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