Subaru Legacy (2005 year). Manual - part 157

EN(H4SO 2.0)(diag)-217

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

13

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

Connector & terminal

LHD model

(E78) No. 4 (+) — Engine ground (

−

):

RHD model

(E78) No. 6 (+) — Engine ground (

−

):

Is the voltage less than 10 V?

Go to step 14.

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

14

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
Measure the voltage between electronic throt-
tle control connector and engine ground.

Connector & terminal

(E78) No. 5 (+) — Engine ground (

−

):

(E78) No. 2 (+) — Engine ground (

−

):

Is the voltage less than 10 V?

Go to step 15.

Repair the short 
circuit of harness 
between ECM 
connector and 
electronic throttle 
control connector.

15

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

Connector & terminal

(B137) No. 23 — (B136) No. 17:
(B137) No. 24 — (B136) No. 17:

Is the resistance more than 1 
M

Ω?

Go to step 16.

Repair the short 
circuit to sensor 
power supply.

16

CHECK ELECTRONIC THROTTLE CON-
TROL HARNESS.
1) Disconnect the connector from ECM.
2) Disconnect the connectors from electronic 
throttle control.
3) Measure the resistance between electronic 
throttle control connector terminals.

Connector & terminal

(E78) No. 5 — (E78) No. 2:

Is the resistance more than 1 
M

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).>

Repair the short 
circuit of harness.

Step

Check

Yes

No

EN(H4SO 2.0)(diag)-218

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

CA:DTC P2138 THROTTLE/PEDAL POSITION SENSOR/SWITCH “D” / “E” 

VOLTAGE CORRELATION

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)-219

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 main accelerator pedal 
position sensor signal and 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.

Go to step 12.

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. 29 — (B315) No. 5:
(B137) No. 25 — (B315) No. 3:
(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

(B137) No. 29 — Chassis ground:
(B137) No. 25 — Chassis ground:
(B137) No. 30 — Chassis ground:
(B136) No. 17 — Chassis ground:

Is the resistance more than 1 
M

Ω?

Go to step 5.

Repair the ground 
short circuit of har-
ness.

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. 3 (+) — Engine ground (

−

):

(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. 3 — No. 4:

Is the resistance 1.2 — 4.8 
k

Ω?

Go to step 7.

Replace the accel-
erator pedal posi-
tion sensor.

7

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 8.

Replace the accel-
erator pedal posi-
tion sensor.

EN(H4SO 2.0)(diag)-220

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

8

CHECK ACCELERATOR PEDAL POSITION 
SENSOR.
Measure the resistance of accelerator pedal 
position sensor without depressing the accel-
erator pedal.

Terminals

No. 5 — No. 4:

Is the resistance 0.2 — 0.8 
k

Ω?

Go to step 9.

Replace the accel-
erator pedal posi-
tion sensor.

9

CHECK ACCELERATOR PEDAL POSITION 
SENSOR.
Measure the resistance of accelerator pedal 
position sensor without depressing the accel-
erator pedal.

Terminals

No. 2 — No. 6:

Is the resistance 0.15 — 0.63 
k

Ω?

Go to step 10.

Replace the accel-
erator pedal posi-
tion sensor.

10

CHECK ACCELERATOR PEDAL POSITION 
SENSOR.
Measure the resistance of accelerator pedal 
position sensor with depressing the accelera-
tor pedal.

Terminals

No. 5 — No. 4:

Is the resistance 0.5 — 2.5 
k

Ω?

Go to step 11.

Replace the accel-
erator pedal posi-
tion sensor.

11

CHECK ACCELERATOR PEDAL POSITION 
SENSOR.
Measure the resistance of accelerator pedal 
position sensor with depressing the accelera-
tor pedal.

Terminals

No. 2 — No. 6:

Is the resistance 0.28 — 1.68 
k

Ω?

Go to step 12.

Replace the accel-
erator pedal posi-
tion sensor.

12

CHECK ACCELERATOR PEDAL POSITION 
SENSOR OUTPUT.
1) Turn the ignition switch to OFF.
2) Connect all the connectors.
3) Turn the ignition switch to ON.
4) Read the data of main throttle sensor signal 
and sub accelerator pedal position sensor sig-
nal 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 13.

Go to step 14.

13

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

Is there poor contact?

Repair the poor 
contact.

Go to step 18.

14

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. 31 — (B315) No. 4:
(B136) No. 18 — (B315) No. 6:

Is the resistance less than 1 
Ω?

Go to step 15.

Repair the open 
circuit of harness 
connector.

Step

Check

Yes

No