Subaru Legacy IV (2008 year). Manual - part 350

EN(H4DOTC)(diag)-221

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BN:DTC P0448 EVAPORATIVE EMISSION CONTROL SYSTEM VENT CONTROL 

CIRCUIT SHORTED

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-126, DTC P0448 EVAPORATIVE EMISSION CON-
TROL SYSTEM VENT CONTROL CIRCUIT SHORTED, Diagnostic Trouble Code (DTC) Detecting Crite-
ria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
52, OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-43, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-05679

SBF-7

E4

B47

E

5
3

6
4

2
1

2

1

C17

C28

D29

C7

R15

R213

R68

R144

R1

B97

14

15

2

2

1

1

7

1

5

E52

2

1

E52

R144

E4

B47

R67

B97

R213

R68

1 2

3

4

1

2

5

6

B21

1 2

1 2

3

4 5 6 7 8

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 26 27 28 29 30 31 32 33

34

35

42

43

36

37

38

39

48

49

50

51

52

53

54

40

41

44

45

46

47

1

2

3 4 5 6

1 2 3 4

5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20

R46

R67

6

B21

E2

11

48

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

B136

C:

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

D:

B136

C:

B137

D:

44

MAIN RELAY

ECM

BATTERY

DRAIN VALVE

PRESSURE 

CONTROL 

SOLENOID VALVE

PURGE CONTROL 

SOLENOID VALVE  1

PURGE CONTROL 

SOLENOID VALVE  2

EN(H4DOTC)(diag)-222

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND 
DRAIN VALVE.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the ECM 
and drain valve.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM and 
chassis ground.

Connector & terminal

(B136) No. 17 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Repair the short 
circuit to the power 
supply in the har-
ness between the 
ECM and drain 
valve connector.

Go to step 2.

2

CHECK DRAIN VALVE.
1) Turn the ignition switch to OFF.
2) Measure the resistance between drain valve 
terminals.

Terminals

No. 1 — No. 2:

Is the resistance less than 1 

:? Replace the drain 

valve. <Ref. to 
EC(H4DOTC)-19, 
Drain Valve.>

Repair the poor 
contact of ECM 
connector.

EN(H4DOTC)(diag)-223

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BO:DTC P0451 EVAPORATIVE EMISSION CONTROL SYSTEM PRESSURE 

SENSOR

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-128, DTC P0451 EVAPORATIVE EMISSION CON-
TROL SYSTEM PRESSURE SENSOR, Diagnostic Trouble Code (DTC) Detecting Criteria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
52, OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-43, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-05095

B83

3

1

2

22

32

30

ECM

B135

R47

R213

R15

R1

B97

B97

1 2 3

R47

B135

7

4

6

6

13

17

B83

R213

FUEL
TANK
PRESSURE
SENSOR

1 2 3 4

5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20

3 4

5 6

1 2

7 8

1 2

3

4 5 6 7 8

 : TERMINAL No. OPTIONAL 
    ARRANGEMENT

*

*

*

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

EN(H4DOTC)(diag)-224

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK FUEL FILLER CAP.
1) Turn the ignition switch to OFF.
2) Open the fuel flap.

Is the fuel filler cap tightened 
securely?

Go to step 2.

Tighten fuel filler 
cap securely.

2

CHECK PRESSURE VACUUM LINE.

NOTE:
Check the following items.
• Disconnection, leakage and clogging of the
vacuum hoses and pipes between fuel tank
pressure sensor and fuel tank
• Disconnection, leakage and clogging of the
air ventilation hoses and pipes between fuel fill-
er pipe and fuel tank

Is there any fault in pressure/
vacuum line?

Repair or replace 
the hoses and 
pipes.

Replace the fuel 
tank pressure sen-
sor. <Ref. to 
EC(H4DOTC)-15, 
Fuel Tank Pres-
sure Sensor.>