Subaru Legacy IV (2008 year). Manual - part 559

EN(H6DO)(diag)-209

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BN:DTC P0301 CYLINDER 1 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-210, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BO:DTC P0302 CYLINDER 2 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-210, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BP:DTC P0303 CYLINDER 3 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-210, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BQ:DTC P0304 CYLINDER 4 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-210, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BR:DTC P0305 CYLINDER 5 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-210, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

5

CHECK HARNESS BETWEEN ECM AND 
FUEL PUMP CONTROL UNIT.
1) Disconnect the connectors from ECM.
2) Measure the resistance of harness between 
ECM and fuel pump control unit.

Connector & terminal

(B136) No. 12 — (R122) No. 8:
(B135) No. 33 — (R122) No. 9:

Is the resistance less than 1 

:? Go to step 6.

Repair the harness 
and connector.

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

6

CHECK HARNESS BETWEEN ECM AND 
FUEL PUMP CONTROL UNIT.
Measure the resistance between fuel pump 
control unit and chassis ground.

Connector & terminal

(R122) No. 8 — Chassis ground:
(R122) No. 9 — Chassis ground:

Is the resistance 1 M

: or 

more?

Go to step 7.

Repair the short 
circuit to ground in 
harness between 
ECM and fuel 
pump control unit 
connector.

7

CHECK POOR CONTACT.
Check for poor contact of ECM and fuel pump 
control unit connector.

Is there poor contact in ECM or 
fuel pump control unit connec-
tor?

Repair the poor 
contact of ECM or 
fuel pump control 
unit connector.

Go to step 8.

8

CHECK EXPERIENCE OF RUNNING OUT OF 
FUEL.

Has the vehicle experienced 
running out of fuel?

Finish the diagno-
sis.

NOTE:
DTC may be re-
corded as a result
of fuel pump idling
while running out
of fuel.

Replace the fuel 
pump control unit. 
<Ref. to 
FU(H6DO)-42, 
Fuel Pump Control 
Unit.>

Step

Check

Yes

No

EN(H6DO)(diag)-210

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BS:DTC P0306 CYLINDER 6 MISFIRE DETECTED

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• Immediately at fault recognition (A misfire which could damage catalyst occurs.)
• GENERAL DESCRIPTION <Ref. to GD(H6DO)-93, DTC P0306 CYLINDER 6 MISFIRE DETECTED, Di-
agnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Engine stalls.
• Improper idling
• Rough driving

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H6DO)(diag)-52,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H6DO)(diag)-44, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

3

4

1

2

5

6

1 2

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

B47

B137

E6

E17

E5

E16

E43

E44

1

2

E5

8

42

B47

MAIN RELAY

1

2

3

5

4

6

48

1

2

E16

1

2

E6

10

ECM

BATTERY

SBF-7

B137

9

43

44

FUEL

INJECTOR 

No. 1

1

2

E17

1

2

E43

11

45

12

46

1

2

E44

E

B21

E2

13

47

EN-06776

B21

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

FUEL

INJECTOR 

No. 2

FUEL

INJECTOR 

No. 3

FUEL

INJECTOR 

No. 4

FUEL

INJECTOR 

No. 5

FUEL

INJECTOR 

No. 6

EN(H6DO)(diag)-211

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 on faulty cylinders.

Connector & terminal

#1 (B137) No. 8 (+) — Chassis ground (–):
#2 (B137) No. 9 (+) — Chassis ground (–):
#3 (B137) No. 10 (+) — Chassis ground (–):
#4 (B137) No. 11 (+) — Chassis ground (–):
#5 (B137) No. 12 (+) — Chassis ground (–):
#6 (B137) No. 13 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step 6.

Go to step 2.

2

CHECK HARNESS BETWEEN ECM AND 
FUEL INJECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector 
on faulty cylinders.
3) Measure the resistance between fuel injec-
tor connector and engine ground on faulty cylin-
ders.

Connector & terminal

#1 (E5) No. 1 — Engine ground:
#2 (E16) No. 1 — Engine ground:
#3 (E6) No. 1 — Engine ground:
#4 (E17) No. 1 — Engine ground:
#5 (E43) No. 1 — Engine ground:
#6 (E44) 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 fuel 
injector.

3

CHECK HARNESS BETWEEN ECM AND 
FUEL INJECTOR.
Measure the resistance of harness between 
ECM and fuel injector on faulty cylinders.

Connector & terminal

#1 (B137) No. 8 — (E5) No. 1:
#2 (B137) No. 9 — (E16) No. 1:
#3 (B137) No. 10 — (E6) No. 1:
#4 (B137) No. 11 — (E17) No. 1:
#5 (B137) No. 12 — (E43) No. 1:
#6 (B137) No. 13 — (E44) No. 1:

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 of
harness between
ECM and fuel in-
jector connector
• Poor contact of
coupling connector

4

CHECK FUEL INJECTOR.
Measure the resistance between fuel injector 
terminals on faulty cylinder.

Terminals

No. 1 — No. 2:

Is the resistance between 5 — 
20 

:?

Go to step 5.

Replace the faulty 
fuel injector. <Ref. 
to FU(H6DO)-28, 
Fuel Injector.>

5

CHECK POWER SUPPLY LINE.
1) Turn the ignition switch to ON.
2) Measure the voltage between fuel injector 
and engine ground on faulty cylinders.

Connector & terminal

#1 (E5) No. 2 (+) — Engine ground (–):
#2 (E16) No. 2 (+) — Engine ground (–):
#3 (E6) No. 2 (+) — Engine ground (–):
#4 (E17) No. 2 (+) — Engine ground (–):
#5 (E43) No. 2 (+) — Engine ground (–):
#6 (E44) No. 2 (+) — Engine ground (–):

Is the voltage 10 V or more?

Repair the poor 
contact of all con-
nectors in fuel 
injector circuit.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
the main relay and
fuel injector on
faulty cylinders
• Poor contact of
coupling connector
• Poor contact of
main relay connec-
tor

EN(H6DO)(diag)-212

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

6

CHECK HARNESS BETWEEN ECM AND 
FUEL INJECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector 
on faulty cylinders.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM and 
chassis ground on faulty cylinders.

Connector & terminal

#1 (B137) No. 8 (+) — Chassis ground (–):
#2 (B137) No. 9 (+) — Chassis ground (–):
#3 (B137) No. 10 (+) — Chassis ground (–):
#4 (B137) No. 11 (+) — Chassis ground (–):
#5 (B137) No. 12 (+) — Chassis ground (–):
#6 (B137) No. 13 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Repair the short 
circuit to power in 
the harness 
between the ECM 
and fuel injector.

Go to step 7.

7

CHECK FUEL INJECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between fuel injec-
tor terminals on faulty cylinder.

Terminals

No. 1 — No. 2:

Is the resistance less than 1 

:? Replace the faulty 

fuel injector. <Ref. 
to FU(H6DO)-28, 
Fuel Injector.>

Go to step 8.

8

CHECK INSTALLATION OF CAMSHAFT PO-
SITION SENSOR/CRANKSHAFT POSITION 
SENSOR.

Is the camshaft position sensor 
or crankshaft position sensor 
loosely installed?

Tighten the cam-
shaft position sen-
sor or crankshaft 
position sensor.

Go to step 9.

9

CHECK CRANK PLATE.

Is the crank sprocket rusted or 
the teeth of crank plate broken?

Replace the crank 
plate. <Ref. to 
ME(H6DO)-64, 
Cylinder Block.>

Go to step 10.

10

CHECK INSTALLATION CONDITION OF 
TIMING CHAIN.
Turn the crankshaft using ST, and align the 
alignment mark on crank sprocket with align-
ment mark on cylinder block.
ST

18252AA000

CRANKSHAFT 
SOCKET

Is the timing chain dislocated 
from its proper position?

Correct the instal-
lation condition of 
timing chain. <Ref. 
to ME(H6DO)-46, 
Timing Chain 
Assembly.>

Go to step 11.

11

CHECK FUEL LEVEL.

Is the fuel meter indication 
lower than the “Lower” level?

Refill the fuel so 
that fuel meter indi-
cation is higher 
than the “Lower” 
level. After replen-
ishing fuel, Go to 
step 13.

Go to step 12.

12

CHECK STATUS OF MALFUNCTION INDI-
CATOR LIGHT.
1) Clear the memory using the Subaru Select 
Monitor or general scan tool.

NOTE:
• SUBARU SELECT MONITOR
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H6DO)(diag)-34, Subaru Select Moni-
tor.>
• General Scan Tool
For detailed operation procedures, refer to the
general scan tool operation manual.
2) Start the engine, and drive the vehicle 10 
minutes or more.

Does the malfunction indicator 
light illuminate or blink?

Go to step 14.

Go to step 13.

Step

Check

Yes

No