Subaru Legacy IV (2008 year). Manual - part 353

EN(H4DOTC)(diag)-233

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) Check the fuel filler cap.

NOTE:
The DTC is stored in memory if fuel filler cap is
or was loose or if the cap chain has caught while
tightening.

Is the fuel filler cap tightened 
securely?

Go to step 2.

Tighten fuel filler 
cap securely.

2

CHECK FUEL FILLER CAP.

Is the fuel filler cap genuine?

Go to step 3.

Replace with a 
genuine fuel filler 
cap.

3

CHECK FUEL FILLER PIPE GASKET.

Is there any damage to the seal 
between fuel filler cap and fuel 
filler pipe?

Repair or replace 
the fuel filler cap 
and fuel filler pipe. 
<Ref. to 
FU(H4DOTC)-66, 
Fuel Filler Pipe.>

Go to step 4.

4

CHECK DRAIN VALVE.
1) Connect the delivery (test) mode connector.
2) Turn the ignition switch to ON.
3) Operate the drain valve using the Subaru 
Select Monitor.

NOTE:
Drain valve can be operated using the Subaru
Select Monitor. For the procedures, refer to
“Compulsory Valve Operation Check Mode”.
<Ref. to EN(H4DOTC)(diag)-53, Compulsory
Valve Operation Check Mode.>

Does the drain valve operate?

Go to step 5.

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

5

CHECK PURGE CONTROL SOLENOID 
VALVE.
Operate the purge control solenoid valve using 
the Subaru Select Monitor.

NOTE:
Purge control solenoid valve operation can be
executed using Subaru Select Monitor. For the
procedures, refer to “Compulsory Valve Opera-
tion Check Mode”. <Ref. to EN(H4DOTC)(di-
ag)-53, Compulsory Valve Operation Check
Mode.>

Does the purge control sole-
noid valve operate?

Go to step 6.

Replace the purge 
control solenoid 
valve. <Ref. to 
EC(H4DOTC)-9, 
Purge Control 
Solenoid Valve.>

6

CHECK PRESSURE CONTROL SOLENOID 
VALVE.
Operate the pressure control solenoid valve 
using the Subaru Select Monitor.

NOTE:
The pressure control solenoid valve operation
can be executed using the Subaru Select Mon-
itor. For the procedures, refer to “Compulsory
Valve Operation Check Mode”. <Ref. to
EN(H4DOTC)(diag)-53, Compulsory Valve Op-
eration Check Mode.>

Does the pressure control sole-
noid valve operate?

Go to step 7.

Replace the pres-
sure control sole-
noid valve. <Ref. to 
EC(H4DOTC)-16, 
Pressure Control 
Solenoid Valve.>

7

CHECK EVAPORATIVE EMISSION CON-
TROL SYSTEM LINE.
1) Turn the ignition switch to OFF.
2) Disconnect the delivery (test) mode connec-
tor.

Are there any disconnected, 
broken or clogged evaporation 
lines?

Repair or replace 
the evaporation 
line. <Ref. to 
FU(H4DOTC)-80, 
Fuel Delivery, 
Return and Evapo-
ration Lines.>

Go to step 8.

EN(H4DOTC)(diag)-234

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

8

CHECK CANISTER.

Is the canister damaged?

Repair or replace 
the canister. <Ref. 
to EC(H4DOTC)-7, 
Canister.>

Go to step 9.

9

CHECK FUEL TANK.
Remove the fuel tank. <Ref. to FU(H4DOTC)-
59, Fuel Tank.>

Is the fuel tank damaged?

Repair or replace 
the fuel tank. <Ref. 
to FU(H4DOTC)-
59, Fuel Tank.>

Go to step 10.

10

CHECK ANY OTHER MECHANICAL TROU-
BLE IN EVAPORATIVE EMISSION CON-
TROL SYSTEM.

Are there holes, cracks, clog-
ging, or disconnections, mis-
connection of hoses or pipes in 
evaporative emission control 
system?

Repair or replace 
the hoses or pipes.

Repair the poor 
contact of ECM 
connector.

Step

Check

Yes

No

EN(H4DOTC)(diag)-235

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BT:DTC P0458 EVAPORATIVE EMISSION SYSTEM PURGE CONTROL VALVE 

CIRCUIT LOW

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-134, DTC P0458 EVAPORATIVE EMISSION SYS-
TEM PURGE CONTROL VALVE CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling

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)-236

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM and 
chassis ground.

Connector & terminal

(B137) No. 29 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Repair the poor 
contact of ECM 
connector.

Go to step 2.

2

OPEN CIRCUIT IN HARNESS BETWEEN 
ECM AND PURGE CONTROL SOLENOID 
VALVE.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and 
purge control solenoid valve.
3) Measure the resistance between the purge 
control solenoid valve connector and engine 
ground.

Connector & terminal

(E4) No. 2 — Engine ground:

Is the resistance 1 M

: or 

more?

Go to step 3.

Repair the ground 
short circuit of har-
ness between 
ECM and purge 
control solenoid 
valve connector.

3

OPEN CIRCUIT IN HARNESS BETWEEN 
ECM AND PURGE CONTROL SOLENOID 
VALVE.
Measure the resistance of harness between 
ECM and purge control solenoid valve connec-
tor.

Connector & terminal

(B137) No. 29 — (E4) No. 2:

Is the resistance less than 1 

:? Go to step 4.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and purge
control solenoid
valve connector
• Poor contact of
coupling connector

4

CHECK PURGE CONTROL SOLENOID 
VALVE.
1) Remove the purge control solenoid valve.
2) Measure the resistance between purge con-
trol solenoid valve terminals.

Terminals

No. 1 — No. 2:

Is the resistance between 10 — 
100 

:?

Go to step 5.

Replace the purge 
control solenoid 
valve. <Ref. to 
EC(H4DOTC)-9, 
Purge Control 
Solenoid Valve.>

5

CHECK POWER SUPPLY TO PURGE CON-
TROL SOLENOID VALVE.
1) Turn the ignition switch to ON.
2) Measure the voltage between purge control 
solenoid valve and engine ground.

Connector & terminal

(E4) No. 1 (+) — Engine ground (–):

Is the voltage 10 V or more?

Repair the poor 
contact of purge 
control solenoid 
valve connector.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
main relay and
purge control sole-
noid valve connec-
tor
• Poor contact of
coupling connector
• Poor contact of
main relay connec-
tor