Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 302

EN(H4DOTC)(diag)-432

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.

Connector & terminal

(B135) No. 4 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

2.

Go to step

3.

2

CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.

Is there poor contact of ECM
connector?

Repair the poor
contact of ECM
connector.

Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:

In this case, tem-
porary open or
short circuit of har-
ness or temporary
poor contact of
connector may be
the cause.

3

CHECK POWER SUPPLY TO LEAK CHECK
VALVE ASSEMBLY.
Measure the voltage between the leak check
valve assembly connector and engine ground.

Connector & terminal

(R400) No. 5 (+) — Engine ground (–):

Is the voltage 10 V or more?

Go to step

4.

Repair the power
supply circuit.

4

CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
the leak check valve assembly.
3) Measure the resistance between leak check
valve assembly and chassis ground.

Connector & terminal

(R400) No. 1 — Chassis ground:

Is the resistance 1 MΩ or
more?

Go to step

5.

Repair the short
circuit to ground in
harness between
ECM connector
and leak check
valve assembly
connector.

5

CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
Measure the resistance of harness between
ECM connector and the leak check valve
assembly connector.

Connector & terminal

(B135) No. 4 — (R400) No. 1:

Is the resistance less than 1 Ω? Go to step

6.

Repair the harness
and connector.
NOTE:

In this case, repair
the following item:
• Open circuit in
harness between
ECM

connector

and the leak check
valve

assembly

connector
• Poor contact of
coupling connector

EN(H4DOTC)(diag)-433

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

6

CHECK LEAK CHECK VALVE ASSEMBLY.
Check the switching valve of the leak check
valve assembly. <Ref. to EC(STI)-20, CHECK
SWITCHING VALVE, INSPECTION, Leak
Check Valve Assembly.> <Ref. to EC(w/o STI)-
21, CHECK SWITCHING VALVE, INSPEC-
TION, Leak Check Valve Assembly.>

Is the switching valve of the
leak check valve assembly
OK?

Repair the poor
contact in the leak
check valve
assembly connec-
tor.

Replace the leak
check valve
assembly. <Ref. to
EC(STI)-19, Leak
Check Valve
Assembly.> <Ref.
to EC(w/o STI)-20,
Leak Check Valve
Assembly.>

Step

Check

Yes

No

EN(H4DOTC)(diag)-434

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

FG:DTC P2420 EVAPORATIVE EMISSION SYSTEM SWITCHING VALVE CON-

TROL CIRCUIT HIGH

DTC DETECTING CONDITION:

• Immediately at fault recognition

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-282, DTC P2420 EVAPORATIVE EMISSION SYS-

TEM SWITCHING VALVE CONTROL CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-63,

OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-49, PROCE-

DURE, Inspection Mode.>.

WIRING DIAGRAM:

• Engine electrical system, without SI-DRIVE <Ref. to WI-32, WITHOUT SI-DRIVE, WIRING DIAGRAM,

Engine Electrical System.>

• Engine electrical system, with SI-DRIVE <Ref. to WI-48, WITH SI-DRIVE, WIRING DIAGRAM, Engine

Electrical System.>

ECM

B97

R1

10

B92

2 3 4 5

6 7 8 9

11 12 13 14

17 18 19 20

1

10

15 16

B97

R82

1 2

3 4 5

6 7 8 9 10 11 12

B220

B83

4

1 2 3

6

5

*

B83

*

*

D27

B22

C21

B30

B4

B135

B:

B136

C:

B137

D:

14

17

15

16

13

8

R81

R82

1

5

8

7

6

4

3

R400

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

B135

B:

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

B137

D:

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

B136

C:

1 2

4

5 6 7 8

3

R400

24

23

22

21

B220

13
14

15 16

17

27

24

25
26

20

21
22

23

29
30

31

28

32 35

33
34

37
38

39

36

40

8

9

10

11 12

1

2

5

3

4

7

6

19

18

B220

4

3

EN-09250

R5

B92

E

SBF-7

BATTERY

FUSE

(RELAY BLOCK)

MAIN RELAY

LEAK CHECK VALVE ASSY

VACUUM

PUMP

PRESSURE

SENSOR

SWITCHING

VALVE

: TERMINAL No. OPTIONAL ARRANGEMENT

EN(H4DOTC)(diag)-435

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the leak
check valve assembly.
3) Turn the ignition switch to ON.
4) Measure the voltage between leak check
valve assembly and chassis ground.

Connector & terminal

(R400) No. 1 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Repair the short
circuit to power in
harness between
ECM connector
and leak check
valve assembly
connector.

Go to step

2.

2

CHECK LEAK CHECK VALVE ASSEMBLY.
1) Turn the ignition switch to OFF.
2) Check the switching valve of the leak check
valve assembly. <Ref. to EC(STI)-20, CHECK
SWITCHING VALVE, INSPECTION, Leak
Check Valve Assembly.> <Ref. to EC(w/o STI)-
21, CHECK SWITCHING VALVE, INSPEC-
TION, Leak Check Valve Assembly.>

Is the switching valve of the
leak check valve assembly
OK?

Repair the poor
contact in the leak
check valve
assembly connec-
tor.

Replace the leak
check valve
assembly. <Ref. to
EC(STI)-19, Leak
Check Valve
Assembly.> <Ref.
to EC(w/o STI)-20,
Leak Check Valve
Assembly.>