Subaru Legacy (2005 year). Manual - part 241

EN(H4SO 2.5)(diag)-249

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

7

CHECK SENSOR POWER SUPPLY.
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

(E57) No. 5 (+) — Engine ground (

−

):

Is the voltage 4.5 — 5.5 V?

Go to step 8.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H4SO 2.5)-
37, Engine Con-
trol Module 
(ECM).>

8

CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Turn the ignition switch to OFF.
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 more than 10 
Ω?

Go to step 9.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H4SO 2.5)-
37, Engine Con-
trol Module 
(ECM).>

9

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

NOTE:

For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO 2.5)(diag)-25, Subaru Select Mon-
itor.>

Is the voltage less than 4.63 
V?

Go to step 10.

Go to step 12.

10

CHECK SENSOR OUTPUT.
Read the data of sub throttle sensor signal 
using Subaru Select Monitor.

NOTE:

For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO 2.5)(diag)-25, Subaru Select Mon-
itor.>

Is the voltage less than 4.73 
V?

Go to step 11.

Go to step 12.

11

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

Is there poor contact?

Repair the poor 
contact.

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

12

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. 35 — (E57) No. 3:
(B136) No. 18 — (E57) No. 6:
(B136) No. 29 — (E57) No. 4:

Is the resistance less than 1 
Ω?

Go to step 13.

Repair the open 
circuit of harness 
connector.

Step

Check

Yes

No

EN(H4SO 2.5)(diag)-250

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

13

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
1) Connect the ECM connector.
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 
Ω?

Go to step 14.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H4SO 2.5)-
37, Engine Con-
trol Module 
(ECM).>

14

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

(E57) No. 5 (+) — Engine ground (

−

):

Is the voltage less than 10 V?

Go to step 15.

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

15

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

Connector & terminal

(E57) No. 6 (+) — Engine ground (

−

):

(E57) No. 4 (+) — Engine ground (

−

):

Is the voltage less than 10 V?

Go to step 16.

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

16

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

(B136) No. 18 — (B136) No. 16:
(B136) No. 29 — (B136) No. 16:

Is the resistance more than 1 
M

Ω?

Go to step 17.

Repair the short 
circuit to sensor 
power supply.

17

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

(E57) No. 6 — (E57) No. 4:

Is the resistance more than 1 
M

Ω?

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H4SO 2.5)-
37, Engine Con-
trol Module 
(ECM).>

Repair the short 
circuit of harness.

Step

Check

Yes

No

EN(H4SO 2.5)(diag)-251

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

CK: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, conduct Clear Memory Mode <Ref. to EN(H4SO 2.5)(diag)-
40, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO 2.5)(diag)-33, Inspection Mode.>.
WIRING DIAGRAM:
• EC, EK, EH, ER and K4 model

• KA and KS model

NOTE:
Fuel injection system for KA and KS model is the same as 2.0 L model. Refer to EN(H4SO 2.0) section.

EN-03468

B315

ACCELERATOR

PEDAL

POSITION

SENSOR

B138

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

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

1 2 3 4 5 6

E

C:

ECM

B136

B137

D:

B83

B315

3

5

4

1

2

6

C15

C17

C34

C16

C28

C35

D1

D2

B21

E2

B1

B138

B122

D3

B: B135

B4

37

36

35

B138

B122

LHD

LHD

RHD

RHD

RHD

LHD

RHD

LHD

*

*

1

1

*

2

*

2

*

2

*

2

*

1

*

1

*

1

*

1

*

: TERMINAL No. RANDOM ARRANGEMENT

1

*

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

2

EN(H4SO 2.5)(diag)-252

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK OPTION CODE.

Is the option code EC, EK, EH, 
ER or K4?

Go to step 2.

Refer to EN(H4SO 
2.0) section. <Ref. 
to EN(H4SO 
2.0)(diag)-64, List 
of Diagnostic Trou-
ble Code (DTC).>

NOTE:
Fuel injection sys-
tem for KA and KS
model is the same
as 2.0 L model.

2

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 2.5)(diag)-25, Subaru Select Mon-
itor.>

Is the voltage more than 0.4 V? Go to step 3.

Go to step 4.

3

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 13.

4

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. 17 — (B315) No. 5:
(B136) No. 15 — (B315) No. 3:
(B136) No. 28 — (B315) No. 2:
(B136) No. 16 — (B315) No. 1:

Is the resistance less than 1 
Ω?

Go to step 5.

Repair the open 
circuit of harness 
connector.

5

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

Connector & terminal

(B136) No. 17 — Chassis ground:
(B136) No. 15 — Chassis ground:
(B136) No. 28 — Chassis ground:
(B136) No. 16 — Chassis ground:

Is the resistance more than 1 
M

Ω?

Go to step 6.

Repair the ground 
short circuit of har-
ness.

6

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 7.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H4SO 2.5)-
37, Engine Con-
trol Module 
(ECM).>