Subaru Legacy IV (2008 year). Manual - part 378

EN(H4DOTC)(diag)-333

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DX:DTC P2128 THROTTLE/PEDAL POSITION SENSOR/SWITCH “E” CIRCUIT 

HIGH INPUT

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-220, DTC P2128 THROTTLE/PEDAL POSITION
SENSOR/SWITCH “E” 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(H4DOTC)(diag)-
52, OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-43, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-05690

B315

C: B136

B137

D:

B83

B315

*

*

4

6

5

1

3

2

B21

B23

B29

B22

B31

B30

D2

B21

E2

D1

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:

C:

D:

B122

B83

D3

A5

C6

B: B135

A: B134

D7

37

35

34

40

36

B122

1 2 3 4 5 6

*

*

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

A:

E

*

ACCELERATOR PEDAL 

POSITION SENSOR

ECM

: TERMINAL No. OPTIONAL 
  ARRANGEMENT

EN(H4DOTC)(diag)-334

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. 31 — (B315) No. 3:
(B135) No. 30 — (B315) No. 2:

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 ECM.
2) Measure the resistance between accelera-
tor pedal position sensor connector and chassis 
ground.

Connector & terminal

(B315) No. 2 — Chassis ground:

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 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. 3 (+) — 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. 22 — (B135) No. 31:

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(H4DOTC)(diag)-335

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DY:DTC P2135 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A”/“B” 

VOLTAGE CORRELATION

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-222, DTC P2135 THROTTLE/PEDAL POSITION
SENSOR/SWITCH “A”/“B” VOLTAGE CORRELATION, 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(H4DOTC)(diag)-
52, OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-43, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-05673

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

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

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

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

1 2 3 4 5 6

E57

B47

B137

D:

B21

B122

B136

C:

B362

B134

A:

36

40

34

35

37

E2

B21

C21

C1

A29

6

A18

C6

A28

6

4

25

*

*

B122

24

E

38

39

28

D5

D4

A19

A5

D7

D1

D2

D3

3

E57

2

1

5

B134

B362

B47

5

7

6

A:

B137

B136

D:

C:

*

E

SBF-7

8

6

4

E

3

4

1

2

5

6

ELECTRONIC
THROTTLE 
CONTROL RELAY

MAIN RELAY

BATTERY

ECM

ELECTRONIC THROTTLE 
CONTROL

: TERMINAL No. OPTIONAL 
  ARRANGEMENT

EN(H4DOTC)(diag)-336

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

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

Connector & terminal

(B134) No. 19 — Chassis ground:
(B134) No. 18 — Chassis ground:
(B134) No. 18 — (B136) No. 6:
(B134) No. 28 — Chassis ground:

Is the resistance 1 M

: or 

more?

Go to step 2.

Repair the short 
circuit to ground in 
harness between 
ECM and elec-
tronic throttle con-
trol connector.

2

CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Connect the ECM.
2) Measure the resistance between electronic 
throttle control connector and engine ground.

Connector & terminal

(E57) No. 6 — Engine ground:
(E57) No. 4 — Engine ground:

Is the resistance 1 M

: or 

more?

Go to step 3.

Repair the short 
circuit to ground in 
harness between 
ECM and elec-
tronic throttle con-
trol connector. 
Replace the ECM if 
defective. <Ref. to 
FU(H4DOTC)-52, 
Engine Control 
Module (ECM).>

3

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Disconnect the connectors from ECM.
2) Measure the resistance of harness between 
ECM and electronic throttle control connector.

Connector & terminal

(B134) No. 18 — (E57) No. 6:
(B134) No. 28 — (E57) No. 4:
(B134) No. 29 — (E57) No. 3:

Is the resistance less than 1 

:? Go to step 4.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and electron-
ic throttle control
connector
• Poor contact of
coupling connector

4

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Connect the ECM.
2) Measure the resistance between electronic 
throttle control connector and engine ground.

Connector & terminal

(E57) No. 3 — Engine ground:

Is the resistance less than 5 

:? Go to step 5.

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

5

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 (–):
(E57) No. 4 (+) — Engine ground (–):

Is the voltage 4.85 V or more?

Repair the short 
circuit to power in 
the harness 
between ECM and 
electronic throttle 
control connector.

Go to step 6.