Subaru Legacy III (2000-2003 year). Manual - part 319

EN(H6DO)-78

ENGINE (DIAGNOSTICS)

DIAGNOSTICS FOR ENGINE STARTING FAILURE

6

CHECK INPUT VOLTAGE OF MAIN RELAY.
Check voltage between main relay connector 
and chassis ground.

Connector & terminal

(B47) No. 2 (+) — Chassis ground (–):

Does the measured value exceed the specified 
value?

10 V

Go to step 7.

Repair open circuit 
in harness 
between ECM 
connector and 
main relay con-
nector.

7

CHECK GROUND CIRCUIT OF MAIN RE-
LAY.
1) Turn ignition switch to OFF.
2) Measure resistance between main relay 

connector and chassis ground.

Connector & terminal

(B47) No. 1 — Chassis ground:

Is the measured value less than the speci-
fied value?

5 

Ω

Go to step 8.

Repair open circuit 
between main 
relay and chassis 
ground.

8

CHECK INPUT VOLTAGE OF MAIN RELAY.
Measure voltage between main relay connec-
tor and chassis ground.

Connector & terminal

(B47) No. 5 (+) — Chassis ground (

−−−−

):

(B47) No. 6 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the specified 
value?

10 V

Go to step 9.

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

9

CHECK INPUT VOLTAGE OF ECM.
1) Connect main relay connector.
2) Turn ignition switch to ON.
3) Measure voltage between ECM connector 

and chassis ground.

Connector & terminal

(B137) No. 2 (+) — Chassis ground (–):
(B137) No. 3 (+) — Chassis ground (–):

Does the measured value exceed the spec-
ified value?

10 V

Check ignition 
control system. 
<Ref. to 
EN(H6DO)-80, 
IGNITION CON-
TROL SYSTEM, 
Diagnostics for 
Engine Starting 
Failure.>

Repair open or 
ground short cir-
cuit in harness 
between ECM 
connector and 
main relay con-
nector.

Step

Value

Yes

No

EN(H6DO)-79

ENGINE (DIAGNOSTICS)

DIAGNOSTICS FOR ENGINE STARTING FAILURE

MEMO:

EN(H6DO)-80

ENGINE (DIAGNOSTICS)

DIAGNOSTICS FOR ENGINE STARTING FAILURE

D: IGNITION CONTROL SYSTEM

CAUTION:
After repair or replacement of faulty parts, conduct CLEAR MEMORY MODE <Ref. to EN(H6DO)-54, 
OPERATION, Clear Memory Mode.>  and INSPECTION MODE <Ref. to EN(H6DO)-47, OPERATION, In-
spection Mode.>.
• WIRING DIAGRAM:

EN-00806

E34

E45

E31

E32

E46

E33

B22

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

1
2
3

B136

1 2

7

8 9

5

6

3

4

10 11 12
19 20 21

13 14 15 16

17 18

22 23 24

B72

3 4

1 2

ENGINE CONTROL MODULE

B136

19

23

24

21

20

22

SBF-4

SBF-1

4

1

B72

IGNITION 
SWITCH

NO. 11

E46

E3

B22

E32

6

2

4

1

7

3

2

3

1

2

E34

3

2

E45

3

2

3

5

1

1

1

E31

IGNITION COIL

NO. 1

IGNITION COIL

NO. 2

IGNITION COIL

NO. 3

IGNITION COIL

NO. 4

IGNITION COIL

NO. 5

IGNITION COIL

NO. 6

3

1

2

E33

3

1

2

GE

EN(H6DO)-81

ENGINE (DIAGNOSTICS)

DIAGNOSTICS FOR ENGINE STARTING FAILURE

Step

Value

Yes

No

1

CHECK SPARK PLUG CONDITION.
1) Remove the spark plug. <Ref. to 

IG(H6DO)-4, REMOVAL, Spark Plug.>

2) Check the spark plug condition. <Ref. to 

IG(H6DO)-5, INSPECTION, Spark Plug.>
Is the spark plug OK?

Spark plug is OK.

Go to step 2.

Replace the spark 
plug.

2

CHECK IGNITION SYSTEM FOR SPARKS.
1) Connect spark plug to ignition coil.
2) Lower fuel pressure.
3) Contact spark plug thread portion with 

engine block.

4) While opening throttle valve fully, crank 

engine to check that spark occurs at each 
cylinder.
Does spark occur at each cylinder?

Spark occurs.

Check fuel pump 
system. <Ref. to 
EN(H6DO)-84, 
FUEL PUMP CIR-
CUIT, Diagnostics 
for Engine Start-
ing Failure.>

Go to step 3.

3

CHECK POWER SUPPLY CIRCUIT FOR IG-
NITION COIL & IGNITOR ASSEMBLY.
1) Turn ignition switch to OFF.
2) Disconnect connector from ignition coil & 

ignitor assembly.

3) Turn ignition switch to ON.
4) Measure power supply voltage between 

ignition coil & ignitor assembly 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 (

−−−−

):

(E45) No. 3 (+) — Engine ground (

−−−−

):

(E46) No. 3 (+) — Engine ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 4.

Repair harness 
and connector.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
ignition coil & igni-
tor assembly, and 
ignition switch 
connector
• Poor contact in 
coupling connec-
tors

4

CHECK HARNESS OF IGNITION COIL & IG-
NITOR ASSEMBLY GROUND CIRCUIT.
1) Turn ignition switch to OFF.
2) Measure resistance between ignition coil & 

ignitor assembly 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:
(E45) No. 2 — Engine ground:
(E46) No. 2 — Engine ground:

Is the measured value less than the speci-
fied value?

5 

Ω

Go to step 5.

Repair harness 
and connector.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
ignition coil & igni-
tor assembly con-
nector and engine 
grounding terminal