Subaru Legacy IV (2008 year). Manual - part 121

EN(H4SO)(diag)-87

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

20.Diagnostic Procedure with Diagnostic Trouble Code (DTC)

A: DTC P0026 INTAKE VALVE CONTROL SOLENOID CIRCUIT RANGE/

PERFORMANCE (BANK 1)

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-8, DTC P0026 INTAKE VALVE CONTROL SOLENOID
CIRCUIT RANGE/PERFORMANCE (BANK 1), 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(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-04025

B134

31

B21

E2

21

ECM

B21

1

VVL DIAGNOSIS

 OIL PRESSURE SWITCH

 RH

E71

B134

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

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

EN(H4SO)(diag)-88

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND 
VARIABLE VALVE LIFT DIAGNOSIS OIL 
PRESSURE SWITCH.
1) Warm up the engine.
2) Turn the ignition switch to OFF.
3) Disconnect the connectors from ECM and 
variable valve lift diagnosis oil pressure switch.
4) Measure the resistance of harness between 
ECM and variable valve lift diagnosis oil pres-
sure switch connector.

Connector & terminal

(B134) No. 31 — (E71) No. 1:

Is the resistance less than 1 

:? Go to step 2.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and variable
valve lift diagnosis
oil pressure switch
connector
• Poor contact of
coupling connector

2

CHECK HARNESS BETWEEN ECM AND 
VARIABLE VALVE LIFT DIAGNOSIS OIL 
PRESSURE SWITCH.
Measure the resistance between variable valve 
lift diagnosis oil pressure switch connector and 
engine ground.

Connector & terminal

(E71) No. 1 — Engine ground:

Is the resistance 1 M

: or 

more?

Go to step 3.

Repair the ground 
short circuit of har-
ness between 
ECM and variable 
valve lift diagnosis 
oil pressure switch 
connector.

3

CHECK HARNESS BETWEEN ECM AND 
VARIABLE VALVE LIFT DIAGNOSIS OIL 
PRESSURE SWITCH.
1) Turn the ignition switch to ON.
2) Measure the voltage between variable valve 
lift diagnosis oil pressure switch connector and 
engine ground.

Connector & terminal

(E71) No. 1 (+) — Engine ground (–):

Is the voltage 10 V or more?

Repair the short 
circuit of harness 
to power supply 
between ECM and 
variable valve lift 
diagnosis oil pres-
sure switch con-
nector.

Go to step 4.

4

CHECK DTC.
1) Perform the Clear Memory Mode. 
2) After idling the engine, check the DTC.

NOTE:
For detailed procedure, refer to “Clear Memory
Mode”. <Ref. to EN(H4SO)(diag)-50, Clear
Memory Mode.>

Is DTC displayed?

Replace the oil 
switching solenoid 
valve. <Ref. to 
ME(H4SO)-89, Oil 
Switching Solenoid 
Valve.> Go to step 
5.

End.

5

CHECK DTC.
1) Perform the Clear Memory Mode. 
2) After idling the engine, check the DTC.

NOTE:
For detailed procedure, refer to “Clear Memory
Mode”. <Ref. to EN(H4SO)(diag)-50, Clear
Memory Mode.>

Is DTC displayed?

Check for oil rout-
ing.

End.

EN(H4SO)(diag)-89

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

B: DTC P0028 INTAKE VALVE CONTROL SOLENOID CIRCUIT RANGE/

PERFORMANCE (BANK 2)

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-10, DTC P0028 INTAKE VALVE CONTROL SOLENOID
CIRCUIT RANGE/PERFORMANCE (BANK 2), 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(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-04026

1

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

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

B21

E2

22

B134

32

ECM

VVL DIAGNOSIS

OIL PRESSURE SWITCH LH

E72

B21

B134

EN(H4SO)(diag)-90

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND 
VARIABLE VALVE LIFT DIAGNOSIS OIL 
PRESSURE SWITCH.
1) Warm up the engine.
2) Turn the ignition switch to OFF.
3) Disconnect the connectors from ECM and 
variable valve lift diagnosis oil pressure switch.
4) Measure the resistance of harness between 
ECM and variable valve lift diagnosis oil pres-
sure switch connector.

Connector & terminal

(B134) No. 32 — (E72) No. 1:

Is the resistance less than 1 

:? Go to step 2.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and variable
valve lift diagnosis
oil pressure switch
connector
• Poor contact of
coupling connector

2

CHECK HARNESS BETWEEN ECM AND 
VARIABLE VALVE LIFT DIAGNOSIS OIL 
PRESSURE SWITCH.
Measure the resistance between variable valve 
lift diagnosis oil pressure switch connector and 
engine ground.

Connector & terminal

(E72) No. 1 — Engine ground:

Is the resistance 1 M

: or 

more?

Go to step 3.

Repair the ground 
short circuit of har-
ness between 
ECM and variable 
valve lift diagnosis 
oil pressure switch 
connector.

3

CHECK HARNESS BETWEEN ECM AND 
VARIABLE VALVE LIFT DIAGNOSIS OIL 
PRESSURE SWITCH.
1) Turn the ignition switch to ON.
2) Measure the voltage between variable valve 
lift diagnosis oil pressure switch connector and 
engine ground.

Connector & terminal

(E72) No. 1 (+) — Engine ground (–):

Is the voltage 10 V or more?

Repair the short 
circuit of harness 
to power supply 
between ECM and 
variable valve lift 
diagnosis oil pres-
sure switch con-
nector.

Go to step 4.

4

CHECK DTC.
1) Perform the Clear Memory Mode. 
2) After idling the engine, check the DTC.

NOTE:
For detailed procedure, refer to “Clear Memory
Mode”. <Ref. to EN(H4SO)(diag)-50, Clear
Memory Mode.>

Is DTC displayed?

Replace the oil 
switching solenoid 
valve. <Ref. to 
ME(H4SO)-89, Oil 
Switching Solenoid 
Valve.> Go to step 
5.

End.

5

CHECK DTC.
1) Perform the Clear Memory Mode. 
2) After idling the engine, check the DTC.

NOTE:
For detailed procedure, refer to “Clear Memory
Mode”. <Ref. to EN(H4SO)(diag)-50, Clear
Memory Mode.>

Is DTC displayed?

Check for oil rout-
ing.

End.