Subaru Legacy (2005 year). Manual - part 155

EN(H4SO 2.0)(diag)-209

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK ACCELERATOR PEDAL POSITION 
SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) Read the data of sub accelerator pedal 
position sensor signal using Subaru Select 
Monitor.

NOTE:

For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO 2.0)(diag)-25, Subaru Select Mon-
itor.>

Is the voltage more than 0.4 V? Go to step 2.

Go to step 3.

2

CHECK POOR CONTACT.
Check poor contact in connector between 
ECM and accelerator pedal position sensor.

Is there poor contact?

Repair the poor 
contact.

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

3

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

Connector & terminal

(B137) No. 30 — (B315) No. 2:
(B136) No. 17 — (B315) No. 1:

Is the resistance less than 1 
Ω?

Go to step 4.

Repair the open 
circuit of harness 
connector.

4

CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR.
Measure the resistance between ECM connec-
tor and chassis ground.

Connector & terminal

(B136) No. 30 — Chassis ground:
(B136) No. 17 — Chassis ground:

Is the resistance more than 1 
M

Ω?

Go to step 5.

Repair the chas-
sis short circuit of 
harness.

5

CHECK POWER SUPPLY OF ACCELERA-
TOR PEDAL POSITION SENSOR.
1) Connect the ECM connector.
2) Turn the ignition switch to ON.
3) Measure the voltage between accelerator 
pedal position sensor connector and engine 
ground.

Connector & terminal

(B315) No. 1 (+) — Engine ground (

−

):

Is the voltage 4.5 — 5.5 V?

Go to step 6.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H4SO 2.0)-
34, Engine Con-
trol Module 
(ECM).>

6

CHECK ACCELERATOR PEDAL POSITION 
SENSOR.
Measure the resistance of accelerator pedal 
position sensor.

Terminals

No. 1 — No. 6:

Is the resistance 0.75 — 3.15 
k

Ω?

Go to step 7.

Replace the accel-
erator pedal posi-
tion sensor.

7

CHECK ACCELERATOR PEDAL POSITION 
SENSOR.
1) Measure the resistance of accelerator 
pedal position sensor.

Terminals

No. 2 — No. 6:

2) Check the measured value is within the 
specification without depressing the accelera-
tor pedal.

Is the resistance 0.15 — 0.63 
k

Ω?

Go to step 8.

Replace the accel-
erator pedal posi-
tion sensor.

EN(H4SO 2.0)(diag)-210

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

8

CHECK ACCELERATOR PEDAL POSITION 
SENSOR.
1) Measure the resistance of accelerator 
pedal position sensor.

Terminals

No. 2 — No. 6:

2) Check the measured value is within the 
specification with the accelerator pedal 
depressed.

Is the resistance 0.28 — 1.68 
k

Ω?

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H4SO 2.0)-
34, Engine Con-
trol Module 
(ECM).>

Replace the accel-
erator pedal posi-
tion sensor.

Step

Check

Yes

No

EN(H4SO 2.0)(diag)-211

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

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

HIGH INPUT

DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
• Erroneous idling
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO 2.0)(diag)-
38, OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO 2.0)(diag)-32, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-03486

E

C:

ECM

B136

B137

D:

B315

ACCELERATOR

PEDAL POSITION

SENSOR

3

5

4

1

2

6

D25

D29

D31

C17

D30

C18

C2

C6

B21

E2

C5

B83

1 2 3 4
5 6 7 8

MAIN

SUB

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

B134

A:

C:

D:

B122

B138

D19

C1

A: B134

A2

37

36

35

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 3 4 5 6

B315

D1

MT

AT

AT

B138 :LHD

B122 :RHD

B83

:LHD

B138 :RHD

*

*

*

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

*

*

EN(H4SO 2.0)(diag)-212

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK ACCELERATOR PEDAL POSITION 
SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) Read the data of sub accelerator pedal 
position sensor signal using Subaru Select 
Monitor.

NOTE:

For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO 2.0)(diag)-25, Subaru Select Mon-
itor.>

Is the voltage less than 4.8 V? Go to step 2.

Go to step 3.

2

CHECK POOR CONTACT.
Check poor contact in connector between 
ECM and accelerator pedal position sensor.

Is there poor contact?

Repair the poor 
contact.

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

3

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

Connector & terminal

(B136) No. 18 — (B315) No. 6:

Is the resistance less than 1 
Ω?

Go to step 4.

Repair the open 
circuit of harness 
connector.

4

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

Connector & terminal

(B315) No. 6 — Engine ground:

Is the resistance less than 5 
Ω?

Go to step 5.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H4SO 2.0)-
34, Engine Con-
trol Module 
(ECM).>

5

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

Connector & terminal

(B315) No. 2 (+) — Engine ground (

−

):

Is the voltage less than 6 V?

Go to step 6.

Repair the battery 
short circuit of har-
ness between 
ECM connector 
and accelerator 
pedal position sen-
sor connector.

6

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

Connector & terminal

(B137) No. 30 — (B137) No. 25:
(B137) No. 30 — (B136) No. 17:

Is the resistance more than 1 
M

Ω?

Repair the poor 
contact in acceler-
ator pedal position 
sensor connector. 
Replace the accel-
erator pedal posi-
tion sensor if 
defective.

Repair the short 
circuit to sensor 
power supply.