Subaru Legacy (2005 year). Manual - part 466

EN(H6DO)(diag)-177

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK POWER SUPPLY CIRCUIT TO FUEL 
PUMP CONTROL UNIT.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel pump 
control unit.
3) Turn the ignition switch to ON.
4) Measure the voltage between fuel pump 
control unit and chassis ground.

Connector & terminal

(R122) No. 10 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Go to step 2.

Repair the power 
supply circuit.

NOTE:
In this case, repair
the following:
• Open or ground 
short circuit of har-
ness between fuel 
pump relay and 
fuel pump control 
unit
• Poor contact in 
fuel pump control 
unit connector
• Poor contact in 
fuel pump relay 
connector

2

CHECK GROUND CIRCUIT OF FUEL PUMP 
CONTROL UNIT.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness 
between fuel pump control unit and chassis 
ground.

Connector & terminal

(R122) No. 5 — Chassis ground:

Is the resistance less than 5 
Ω?

Go to step 3.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• Open circuit 
between fuel pump 
control unit and 
chassis ground
• Poor contact in 
fuel pump control 
unit connector

3

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

Connector & terminal

(R122) No. 7 — (R58) No. 5:
(R122) No. 6 — (R58) No. 6:

Is the resistance less than 1 
Ω?

Go to step 4.

Repair the open 
circuit between 
fuel pump control 
unit and fuel 
pump.

4

CHECK HARNESS BETWEEN FUEL PUMP 
CONTROL UNIT AND FUEL PUMP CONNEC-
TOR.
Measure the resistance of harness between 
fuel pump control unit and chassis ground.

Connector & terminal

(R122) No. 7 — Chassis ground:
(R122) No. 6 — Chassis ground:

Is the resistance more than 1 
M

Ω?

Go to step 5.

Repair the ground 
short circuit 
between fuel pump 
control unit and 
fuel pump.

EN(H6DO)(diag)-178

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

5

CHECK HARNESS BETWEEN FUEL PUMP 
CONTROL UNIT AND ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness 
between fuel pump control unit and ECM con-
nector.

Connector & terminal

(R122) No. 9 — (B137) No. 28:
(R122) No. 8 — (B135) No. 27:

Is the resistance less than 1 
Ω?

Go to step 6.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• Open circuit 
between fuel pump 
control unit and 
ECM
• Poor contact in 
fuel pump control 
unit and ECM con-
nector

6

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

Connector & terminal

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

Is the resistance more than 1 
M

Ω?

Go to step 7.

Repair the ground 
short circuit 
between fuel pump 
control unit and 
ECM.

7

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

Is there poor contact in ECM 
and fuel pump control unit con-
nector?

Repair the poor 
contact in ECM 
and fuel pump 
control unit con-
nector.

Go to step 8.

8

CHECK EXPERIENCE OF RUNNING OUT OF 
FUEL.

Has the vehicle experience 
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)-38, 
Fuel Pump Control 
Unit.>

Step

Check

Yes

No

EN(H6DO)(diag)-179

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

AZ:DTC P0301 CYLINDER 1 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-180, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BA:DTC P0302 CYLINDER 2 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-180, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BB:DTC P0303 CYLINDER 3 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-180, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BC:DTC P0304 CYLINDER 4 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-180, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BD:DTC P0305 CYLINDER 5 MISFIRE DETECTED

NOTE:
For the diagnostic procedure, refer to DTC P0306. <Ref. to EN(H6DO)(diag)-180, DTC P0306 CYLINDER 6
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

EN(H6DO)(diag)-180

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

BE:DTC P0306 CYLINDER 6 MISFIRE DETECTED

DTC DETECTING CONDITION:
• Detects when malfunction occurs in 2 continuous driving cycles.
• Immediately at fault recognition (A misfire which could damage catalyst occurs.)
TROUBLE SYMPTOM:
• Engine stalls.
• Erroneous idling
• Rough driving

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)(diag)-41, 
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)(diag)-34, PROCEDURE, 
Inspection Mode.>.
WIRING DIAGRAM:

E6

E17

E5

E16

E43

E44

1

2

1

2

1

2

1

2

4

5

6

3

42

48

43

44

45

ECM

B136

E5

E16

E6

E17

B21

E2

FUEL INJECTOR

No. 1

FUEL INJECTOR

No. 2

FUEL INJECTOR

No. 3

FUEL INJECTOR

No. 4

BATTERY

1

2

1

2

2

1

46

47

E43

E44

FUEL INJECTOR

No. 5

FUEL INJECTOR

No. 6

SBF-7

B47

MAIN RELAY

B47

3

4

1

2

5

6

B136

1 2

EN-03493

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

35

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

E

6
4