Subaru Legacy IV (2008 year). Service manual - part 144

EN(H4SO)(diag)-179

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

23

GROUP OF #1 AND #3 CYLINDERS.

Are there any faults in #1 and 
#3 cylinders?

Repair or replace 
faulty parts.

NOTE:
Check the follow-
ing items.
• Spark plug
• Fuel injector
• Compression ra-
tio
• Skipping timing
belt teeth

Go to DTC P0171. 
<Ref. to 
EN(H4SO)(diag)-
155, DTC P0171 
SYSTEM TOO 
LEAN (BANK 1), 
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code 
(DTC).>

24

GROUP OF #2 AND #4 CYLINDERS.

Are there any faults in #2 and 
#4 cylinders?

Repair or replace 
faulty parts.

NOTE:
Check the follow-
ing items.
• Spark plug
• Fuel injector
• Compression ra-
tio
• Skipping timing
belt teeth

Go to DTC P0171. 
<Ref. to 
EN(H4SO)(diag)-
155, DTC P0171 
SYSTEM TOO 
LEAN (BANK 1), 
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code 
(DTC).>

25

CYLINDER AT RANDOM.

Is the engine idle rough?

Go to DTC P0171. 
<Ref. to 
EN(H4SO)(diag)-
155, DTC P0171 
SYSTEM TOO 
LEAN (BANK 1), 
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code 
(DTC).>

Repair or replace 
faulty parts.

NOTE:
Check the follow-
ing items.
• Spark plug
• Fuel injector
• Compression ra-
tio

Step

Check

Yes

No

EN(H4SO)(diag)-180

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

AX:DTC P0327 KNOCK SENSOR 1 CIRCUIT LOW (BANK 1 OR SINGLE SENSOR)

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-86, DTC P0327 KNOCK SENSOR 1 CIRCUIT LOW
(BANK 1 OR SINGLE SENSOR), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Poor driving performance
• Knocking occurs.

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-04038

15

25

29

1

2

16

19

ECM

B134

B21

E2

E14

E

KNOCK SENSOR

E14

1 2

B21

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

B134

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

33 34

29

32

30 31

EN(H4SO)(diag)-181

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND 
KNOCK SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM.
3) Measure the resistance between ECM con-
nectors.

Connector & terminal

(B134) No. 15 — (B134) No. 29:

Is the resistance 600 k

: or 

more?

Go to step 2.

Repair the poor 
contact of ECM 
connector.

2

CHECK KNOCK SENSOR.
1) Disconnect the connector from knock sen-
sor.
2) Measure the resistance between knock 
sensor terminals.

Terminals

No. 1 — No. 2:

Is the resistance 600 k

: or 

more?

Replace the knock 
sensor. <Ref. to 
FU(H4SO)-25, 
Knock Sensor.>

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and knock
sensor connector
• Poor contact of
the knock sensor
connector
• Poor contact of
coupling connector

EN(H4SO)(diag)-182

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

AY:DTC P0328 KNOCK SENSOR 1 CIRCUIT HIGH (BANK 1 OR SINGLE SENSOR)

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-87, DTC P0328 KNOCK SENSOR 1 CIRCUIT HIGH
(BANK 1 OR SINGLE SENSOR), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Poor driving performance
• Knocking occurs.

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-04038

15

25

29

1

2

16

19

ECM

B134

B21

E2

E14

E

KNOCK SENSOR

E14

1 2

B21

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

B134

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

33 34

29

32

30 31