Subaru Legacy (2005 year). Service manual - part 238

EN(H4SO 2.5)(diag)-237

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

8

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

Terminals

No. 5 — No. 4:

Check the measured value is within the specifi-
cation without depressing the accelerator 
pedal.

Is the resistance 0.2 — 1.0 
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.

Terminals

No. 5 — No. 4:

Check the measured value is within the specifi-
cation with the accelerator pedal depressed.

Is the resistance 0.5 — 2.5 
k

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).>

Replace the accel-
erator pedal posi-
tion sensor.

Step

Check

Yes

No

EN(H4SO 2.5)(diag)-238

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

CG:DTC P2123 THROTTLE/PEDAL POSITION SENSOR/SWITCH “D” 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, 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)-239

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 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 4.8 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.

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

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. 34 — (B315) No. 4:

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

Connector & terminal

(B315) No. 4 — Engine ground:

Is the resistance less than 5 
Ω?

Go to step 6.

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

6

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. 5 (+) — Engine ground (

−

):

Is the voltage less than 6 V?

Go to step 7.

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

EN(H4SO 2.5)(diag)-240

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

7

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

(B136) No. 17 — (B136) No. 15:
(B136) No. 17 — (B136) No. 16:

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.

Step

Check

Yes

No