Subaru Legacy (2005 year). Manual - part 455

EN(H6DO)(diag)-133

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AB:DTC P0122 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT 

LOW

DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
• Erroneous idling
• Engine stalls.
• Poor driving performance
WIRING DIAGRAM:

EN-03499

SBF-7

B135

B:

B137

B136

D:

B362

E1

B20

B83

B122

C:

E

E

E

D6

B35

38

39

20

19

16

15

*
*

E2

B21

E57

4

6

1

2

3

5

D4

D5

C35

C16

B1

B4

D1

D2

D3

36

35

37

C29

C18

ECM

5
6

B362

B20

B21

E57

B122

B83

B138

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

B136

C:

B137

D:

BATTERY

MAIN RELAY

ELECTRONIC
THROTTLE 
CONTROL RELAY

ELECTRONIC
THROTTLE CONTROL

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

1 2 3 4 5 6

*

*

1

*

2

*

2

1

1

1

*

1  : TERMINAL No. 

   RANDOM ARRANGEMENT

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:

8

7

RHD

RHD

LHD

*

: TERMINAL No. 
  RANDOM ARRANGEMENT 
  AMONG 3,4,7, AND 8

2

B122

B138

: LHD

: RHD

EN(H6DO)(diag)-134

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) 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(H6DO)(diag)-26, Subaru Select Moni-
tor.>

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 electronic throttle control.

Is there poor contact in con-
nector between ECM and elec-
tronic throttle control?

Repair the poor 
contact.

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

3

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. 18 — (E57) No. 6:
(B136) No. 16 — (E57) No. 5:

Is the resistance less than 1 
Ω?

Go to step 4.

Repair the open 
circuit of harness 
connector.

4

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
Measure the resistance between ECM connec-
tor and chassis ground.

Connector & terminal

(B136) No. 18 — Chassis ground:
(B136) No. 16 — 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 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 4.5 — 5.5 V?

Go to step 6.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H6DO)-34, 
Engine Control 
Module (ECM).>

6

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:

Is the resistance more than 10 
Ω?

Repair the poor 
contact of elec-
tronic throttle con-
trol connector. 
Replace the accel-
erator pedal posi-
tion sensor if 
defective.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H6DO)-34, 
Engine Control 
Module (ECM).>

EN(H6DO)(diag)-135

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AC:DTC P0123 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT 

HIGH

DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
• Erroneous idling
• Engine stalls.
• Poor driving performance
WIRING DIAGRAM:

EN-03499

SBF-7

B135

B:

B137

B136

D:

B362

E1

B20

B83

B122

C:

E

E

E

D6

B35

38

39

20

19

16

15

*
*

E2

B21

E57

4

6

1

2

3

5

D4

D5

C35

C16

B1

B4

D1

D2

D3

36

35

37

C29

C18

ECM

5
6

B362

B20

B21

E57

B122

B83

B138

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

B136

C:

B137

D:

BATTERY

MAIN RELAY

ELECTRONIC
THROTTLE 
CONTROL RELAY

ELECTRONIC
THROTTLE CONTROL

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

1 2 3 4 5 6

*

*

1

*

2

*

2

1

1

1

*

1  : TERMINAL No. 

   RANDOM ARRANGEMENT

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:

8

7

RHD

RHD

LHD

*

: TERMINAL No. 
  RANDOM ARRANGEMENT 
  AMONG 3,4,7, AND 8

2

B122

B138

: LHD

: RHD

EN(H6DO)(diag)-136

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) 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(H6DO)(diag)-26, Subaru Select Moni-
tor.>

Is the voltage less than 4.63 
V?

Go to step 2.

Go to step 3.

2

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

Is there poor contact in con-
nector between ECM and elec-
tronic throttle control?

Repair the poor 
contact.

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

3

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

Is the resistance less than 1 
Ω?

Go to step 4.

Repair the open 
circuit of harness 
connector.

4

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 1 
Ω?

Go to step 5.

Repair the poor 
contact in ECM 
connector. 
Replace the ECM 
if defective. <Ref. 
to FU(H6DO)-34, 
Engine Control 
Module (ECM).>

5

CHECK SENSOR OUTPUT POWER SUP-
PLY.
Measure the voltage between electronic throt-
tle control connector and engine ground.

Connector & terminal

(E57) No. 6 (+) — Engine ground (

−

):

Is the voltage less than 10 V?

Go to step 6.

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

6

CHECK HARNESS BETWEEN ECM AND 
ELECTRONIC THROTTLE CONTROL.
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. 18 — (B136) No. 16:

Is the resistance more than 1 
M

Ω?

Repair the poor 
contact in harness. 
Repair the elec-
tronic throttle con-
trol.

Repair the short 
circuit to sensor 
power supply.