Subaru Legacy (2005 year). Service manual — part 321

EN(H4DOTC)(diag)-53

ENGINE (DIAGNOSTICS)

Diagnostics for Engine Starting Failure

C: CHECK POWER SUPPLY AND GROUND LINE OF ENGINE CONTROL MOD-

ULE (ECM)

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
37, OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOTC)(diag)-30, PROCE-
DURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-03519

B72

BATTERY

MAIN RELAY

SBF-6

MAIN SBF

SBF-7

No.13

SBF-5

B72

TO FRONT OXYGEN(A/F) SENSOR

D16

A6

A7

B1

B4

D7

B12

D1

D2

D3

B5

B6

B19

D14

No.12

B47

E2

B21

2

1

4

6

5

3

ECM

E

E

3

6

B134

B135

B137

A:

B:

D:

54

35

36

12

34

3

4

1

2

5

6

B47

B21

B134

A:

B137

D:

B135

B:

IGNITION
SWITCH

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

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

29 30 31

32 33

34 35

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

37

1

3

4 5 6

2

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

EN(H4DOTC)(diag)-54

ENGINE (DIAGNOSTICS)

Diagnostics for Engine Starting Failure

Step

Check

Yes

No

1

CHECK MAIN RELAY.
1) Turn the ignition switch to OFF.
2) Remove the main relay.
3) Connect the battery to main relay terminals
No. 1 and No. 2.
4) Measure the resistance between main relay
terminals.

Terminals

No. 3 — No. 5:
No. 4 — No. 6:

Is the resistance less than 10
Ω?

Go to step 2.

Replace the main
relay.

2

CHECK GROUND CIRCUIT FOR ECM.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness
between ECM and chassis ground.

Connector & terminal

(B134) No. 6 — Chassis ground:
(B134) No. 7 — Chassis ground:
(B135) No. 1 — Chassis ground:
(B135) No. 4 — Chassis ground:
(B135) No. 12 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 2 — Chassis ground:
(B137) No. 3 — Chassis ground:
(B137) No. 7 — Chassis ground:

Is the resistance less than 5
Ω?

Go to step 3.

Repair the open
circuit of harness
between ECM
connector and
engine grounding
terminal.

3

CHECK INPUT VOLTAGE OF ECM.
Measure the voltage between ECM connector
and chassis ground.

Connector & terminal

(B135) No. 19 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Go to step 4.

Repair the open or
ground short cir-
cuit of power sup-
ply circuit.

4

CHECK INPUT VOLTAGE OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM con-
nector and chassis ground.

Connector & terminal

(B137) No. 14 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Go to step 5.

Repair the open or
ground short cir-
cuit of power sup-
ply circuit.

5

CHECK INPUT VOLTAGE OF MAIN RELAY.
Measure the voltage between main relay con-
nector and chassis ground.

Connector & terminal

(B47) No. 2 (+) — Chassis ground (

−

):

(B47) No. 5 (+) — Chassis ground (

−

):

(B47) No. 6 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Go to step 6.

Repair the open or
ground short cir-
cuit of harness of
power supply cir-
cuit.

6

CHECK INPUT VOLTAGE OF ECM.
1) Connect the main relay connector.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM con-
nector and chassis ground.

Connector & terminal

(B135) No. 5 (+) — Chassis ground (

−

):

(B135) No. 6 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Check ignition

control system.
<Ref. to
EN(H4DOTC)(diag
)-55, IGNITION
CONTROL SYS-
TEM, Diagnostics
for Engine Start-
ing Failure.>

Repair the open or
ground short cir-
cuit of harness
between ECM
connector and
main relay connec-
tor.

EN(H4DOTC)(diag)-55

ENGINE (DIAGNOSTICS)

Diagnostics for Engine Starting Failure

D: IGNITION CONTROL SYSTEM

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
37, OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOTC)(diag)-30, PROCE-
DURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-03520

SBF-6

MAIN SBF

B72

B135

18

17

16

15

ECM

No.12

E

E

6

3

E2

B21

E31

E31

E32

E33

E34

No.1

E32

E33

E34

1
2
3

B21

3

1

2

3

1

2

13

49

14

15

16

3

1

2

3

1

2

IGNITION
SWITCH

IGNITION COIL

No.2

IGNITION COIL

No.3

IGNITION COIL

No.4

IGNITION COIL

B135

B72

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

29 30 31

32 33

34 35

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

1

3

4 5 6

2

EN(H4DOTC)(diag)-56

ENGINE (DIAGNOSTICS)

Diagnostics for Engine Starting Failure

Step

Check

Yes

No

1

CHECK CONDITION OF SPARK PLUG.
1) Remove the spark plug. <Ref. to
IG(H4DOTC)-4, REMOVAL, Spark Plug.>
2) Check the spark plug condition. <Ref. to
IG(H4DOTC)-5, INSPECTION, Spark Plug.>

Is the spark plug in normal
condition?

Go to step 2.

Replace the spark
plug.

2

CHECK SPARK OF IGNITION SYSTEM.
1) Connect the spark plug to ignition coil.
2) Release the fuel pressure. <Ref. to
FU(H4DOTC)-39, RELEASING OF FUEL
PRESSURE, PROCEDURE, Fuel.>
3) Contact the spark plug thread portion on
engine.
4) While opening the throttle valve fully, crank
the engine to check that spark occurs at each
cylinder.

Does spark occur at each cyl-
inder?

Check the fuel
pump system.
<Ref. to
EN(H4DOTC)(diag
)-58, FUEL PUMP
CIRCUIT, Diag-
nostics for Engine
Starting Failure.>

Go to step 3.

3

CHECK POWER SUPPLY CIRCUIT OF IGNI-
TION COIL.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ignition coil.
3) Turn the ignition switch to ON.
4) Measure the power supply voltage between
ignition coil connector and engine ground.

Connector & terminal

(E31) No. 3 (+) — Engine ground (

−

):

(E32) No. 3 (+) — Engine ground (

−

):

(E33) No. 3 (+) — Engine ground (

−

):

(E34) No. 3 (+) — Engine ground (

−

):

Is the voltage more than 10 V? Go to step 4.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• Open circuit of
harness between
ignition coil and
ignition switch con-
nector
• Poor contact in
coupling connector

4

CHECK HARNESS OF IGNITION COIL
GROUND CIRCUIT.
1) Turn the ignition switch to OFF.
2) Measure the resistance between ignition
coil connector and engine ground.

Connector & terminal

(E31) No. 2 — Engine ground:
(E32) No. 2 — Engine ground:
(E33) No. 2 — Engine ground:
(E34) No. 2 — Engine ground:

Is the resistance less than 5
Ω?

Go to step 5.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• Open circuit of
harness between
ignition coil con-
nector and engine
ground terminal

5

CHECK HARNESS BETWEEN ECM AND IG-
NITION COIL CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Disconnect the connector from ignition coil.
4) Measure the resistance of harness
between ECM and ignition coil connector.

Connector & terminal

(B135) No. 15 — (E34) No. 1:
(B135) No. 16 — (E33) No. 1:
(B135) No. 17 — (E32) No. 1:
(B135) No. 18 — (E31) No. 1:

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 of
harness between
ECM and ignition
coil connector
• Poor contact in
coupling connector

6

CHECK HARNESS BETWEEN ECM AND IG-
NITION COIL CONNECTOR.
Measure the resistance of harness between
ECM and engine ground.

Connector & terminal

(B135) No. 15 — Engine ground:
(B135) No. 16 — Engine ground:
(B135) No. 17 — Engine ground:
(B135) No. 18 — Engine ground:

Is the resistance more than 1
M

Ω?

Go to step 7.

Repair the ground
short circuit of har-
ness between
ECM and ignition
coil connector.