Subaru Legacy IV (2008 year). Manual - part 155

EN(H4SO)(diag)-223

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BU:DTC P0506 IDLE AIR CONTROL SYSTEM RPM LOWER THAN EXPECTED

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-139, DTC P0506 IDLE AIR CONTROL SYSTEM RPM
LOWER THAN EXPECTED, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Hard to start the engine.
• Engine does not start.
• Improper idling
• Engine stalls.

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-06838

SBF-7

B134

A:

B137

B136

D:

B362

C:

E

C1

C21

D4

D5

A29

A19

D3

D7

D1

D2

A5

A28

A18

C6

ECM

5

8

7

6

B362

B47

B21

E57

B122

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

B134

A:

B136

C:

B137

D:

BATTERY

ELECTRONIC 
THROTTLE 
CONTROL RELAY

MAIN RELAY

1 2 3 4 5 6

E2

B21

B122

E

E

E

39

20

E57

4

6

1

2

3

5

34

35

36

37

52

*
*

ELECTRONIC 
THROTTLE CONTROL

: TERMINAL No. OPTIONAL ARRANGEMENT

*

18

17

38

19

8

5

6

10 11 12 13 14 15

7

2

1

3

4

16

30

19 20

22

28 29

9

17

18

25

21

23 24

32

31

26 27
33 34

3

4

1

2

5

6

6

4

B47

EN(H4SO)(diag)-224

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?

Check the appro-
priate DTC using 
the “List of Diag-
nostic Trouble 
Code (DTC)”. 
<Ref. to 
EN(H4SO)(diag)-
80, List of Diagnos-
tic Trouble Code 
(DTC).>

Go to step 2.

2

CHECK AIR CLEANER ELEMENT.
1) Turn the ignition switch to OFF.
2) Check the air cleaner element.

Is the air cleaner element 
excessively clogged?

Replace the air 
cleaner element. 
<Ref. to IN(H4SO)-
4, Air Cleaner Ele-
ment.>

Go to step 3.

3

CHECK ELECTRONIC THROTTLE CON-
TROL.
1) Remove the electronic throttle control.
2) Check the electronic throttle control.

Are foreign matter found inside 
electronic throttle control?

Remove foreign 
matter from elec-
tronic throttle con-
trol.

Perform the diag-
nosis of DTC 
P2101. <Ref. to 
EN(H4SO)(diag)-
276, DTC P2101 
THROTTLE 
ACTUATOR CON-
TROL MOTOR 
CIRCUIT RANGE/
PERFORMANCE, 
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code 
(DTC).>

EN(H4SO)(diag)-225

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BV:DTC P0507 IDLE AIR CONTROL SYSTEM RPM HIGHER THAN EXPECTED

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-140, DTC P0507 IDLE AIR CONTROL SYSTEM RPM
HIGHER THAN EXPECTED, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine keeps running at higher speed than specified idle speed.

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-06838

SBF-7

B134

A:

B137

B136

D:

B362

C:

E

C1

C21

D4

D5

A29

A19

D3

D7

D1

D2

A5

A28

A18

C6

ECM

5

8

7

6

B362

B47

B21

E57

B122

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

B134

A:

B136

C:

B137

D:

BATTERY

ELECTRONIC 
THROTTLE 
CONTROL RELAY

MAIN RELAY

1 2 3 4 5 6

E2

B21

B122

E

E

E

39

20

E57

4

6

1

2

3

5

34

35

36

37

52

*
*

ELECTRONIC 
THROTTLE CONTROL

: TERMINAL No. OPTIONAL ARRANGEMENT

*

18

17

38

19

8

5

6

10 11 12 13 14 15

7

2

1

3

4

16

30

19 20

22

28 29

9

17

18

25

21

23 24

32

31

26 27
33 34

3

4

1

2

5

6

6

4

B47

EN(H4SO)(diag)-226

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?

Check the appro-
priate DTC using 
the “List of Diag-
nostic Trouble 
Code (DTC)”. 
<Ref. to 
EN(H4SO)(diag)-
80, List of Diagnos-
tic Trouble Code 
(DTC).>

Go to step 2.

2

CHECK AIR INTAKE SYSTEM.
1) Start and idle the engine.
2) Check the following items.
• Loose installation of intake manifold and 
throttle body
• Cracks of intake manifold gasket and throttle 
body gasket
• Disconnection of vacuum hoses

Is there any fault in air intake 
system?

Repair air suction 
and leaks.

Go to step 3.

3

CHECK ELECTRONIC THROTTLE CON-
TROL.
1) Turn the ignition switch to OFF.
2) Remove the electronic throttle control.
3) Check the electronic throttle control.

Are foreign matter found inside 
electronic throttle control?

Remove foreign 
matter from elec-
tronic throttle con-
trol.

Perform the diag-
nosis of DTC 
P2101. <Ref. to 
EN(H4SO)(diag)-
276, DTC P2101 
THROTTLE 
ACTUATOR CON-
TROL MOTOR 
CIRCUIT RANGE/
PERFORMANCE, 
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code 
(DTC).>