Subaru Legacy IV (2008 year). Service manual — part 171

EN(H4SO)(diag)-287

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DF:DTC P2123 THROTTLE/PEDAL POSITION SENSOR/SWITCH “D” CIRCUIT

HIGH INPUT

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-188, DTC P2123 THROTTLE/PEDAL POSITION SEN-
SOR/SWITCH “D” CIRCUIT HIGH INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Improper idling
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-06844

B315

E

C:

ECM

B136

B137

D:

B83

B315

*

*

4

6

5

1

3

2

D1

D2

1 2 3 4 5 6

B21

E2

D3

B122

1 2 3 4
5 6 7 8

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

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

B136

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

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

B:

B134

A:

C:

D:

B83

A5

B: B135

A: B134

D7

36

34

52

35

37

B122

ACCELERATOR

PEDAL

POSITION

SENSOR

E

*

*

: TERMINAL No. OPTIONAL
ARRANGEMENT

*

B21

B23

B29

B22

B31

B30

C6

8

5

6

10 11 12 13 14 15

7

2

1

3

4

16

30

19 20

22

28 29

9

17

18

25

21

23 24

32

31

26 27
33 34

EN(H4SO)(diag)-288

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
accelerator pedal position sensor.
3) Measure the resistance of harness between
ECM and accelerator pedal position sensor
connector.

Connector & terminal

(B135) No. 23 — (B315) No. 6:
(B135) No. 29 — (B315) No. 5:

Is the resistance less than 1

:? Go to step 2.

Repair the open
circuit in harness
between ECM and
accelerator pedal
position sensor
connector.

2

CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR.
1) Connect the connector to ECM.
2) Measure the resistance between accelera-
tor pedal position sensor connector and chassis
ground.

Connector & terminal

(B315) No. 5 — Chassis ground:

Is the resistance less than 5

:? Go to step 3.

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

3

CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between accelerator
pedal position sensor connector and chassis
ground.

Connector & terminal

(B315) No. 6 (+) — Chassis ground (–):

Is the voltage 4.85 V or more?

Repair the short
circuit of harness
to power supply
between ECM and
accelerator pedal
position sensor
connector.

Go to step 4.

4

CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM.
3) Measure the resistance between ECM con-
nectors.

Connector & terminal

(B135) No. 21 — (B135) No. 23:

Is the resistance 1 M

: or

more?

Repair the poor
contact of acceler-
ator pedal position
sensor connector.
Replace the accel-
erator pedal if
defective. <Ref. to
SP(H4SO)-3,
Accelerator
Pedal.>

Repair the short
circuit of harness
to power supply
between ECM and
accelerator pedal
position sensor
connector.

EN(H4SO)(diag)-289

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DG:DTC P2127 THROTTLE/PEDAL POSITION SENSOR/SWITCH “E” CIRCUIT

LOW INPUT

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-190, DTC P2127 THROTTLE/PEDAL POSITION SEN-
SOR/SWITCH “E” CIRCUIT LOW INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Improper idling
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-06844

B315

E

C:

ECM

B136

B137

D:

B83

B315

*

*

4

6

5

1

3

2

D1

D2

1 2 3 4 5 6

B21

E2

D3

B122

1 2 3 4
5 6 7 8

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

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

B136

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

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

B:

B134

A:

C:

D:

B83

A5

B: B135

A: B134

D7

36

34

52

35

37

B122

ACCELERATOR

PEDAL

POSITION

SENSOR

E

*

*

: TERMINAL No. OPTIONAL
ARRANGEMENT

*

B21

B23

B29

B22

B31

B30

C6

8

5

6

10 11 12 13 14 15

7

2

1

3

4

16

30

19 20

22

28 29

9

17

18

25

21

23 24

32

31

26 27
33 34

EN(H4SO)(diag)-290

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
accelerator pedal position sensor.
3) Measure the resistance between ECM and
chassis ground.

Connector & terminal

(B135) No. 22 — Chassis ground:
(B135) No. 31 — Chassis ground:

Is the resistance 1 M

: or

more?

Go to step 2.

Repair the ground
short circuit of har-
ness between
ECM and accelera-
tor pedal position
sensor connector.

2

CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Connect the connector to ECM.
2) Measure the resistance between accelera-
tor pedal position sensor connector and chassis
ground.

Connector & terminal

(B315) No. 3 — Chassis ground:

Is the resistance 1 M

: or

more?

Replace the accel-
erator pedal. <Ref.
to SP(H4SO)-3,
Accelerator
Pedal.>

Repair the ground
short circuit of har-
ness between
ECM and accelera-
tor pedal position
sensor connector.
Replace the ECM if
defective. <Ref. to
FU(H4SO)-39,
Engine Control
Module (ECM).>