Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 306

EN(H4DOTC)(diag)-448

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

• Models with SI-DRIVE <Ref. to WI-48, WITH SI-DRIVE, WIRING DIAGRAM, Engine Electrical System.>

Step

Check

Yes

No

1

CHECK SECONDARY AIR COMBINATION
VALVE FUSE.
Check if the secondary air combination valve
fuse (10 A) is blown out.

Is the fuse blown out?

Go to step

2.

Go to step

3.

EN-08735

F9

13

12

11

14

1

2

2

1

3

4

16

15

5

6

B143

F37

B144

B21

E2

E40

E41

B134

A:

A:

B135

B:

B135

B:

B137

D:

F37

F11

F9

10A

60A

9

10

8

7

11

5

20

8

B8

B20
B27
A19

D9

A29

6

1

2

8

47

3

2

1

6

4

1

2

9
2

16
18

14
12
10

4

14

4

B134

46

B220

24

23

22

21

B137

D:

31

30

29

28

27

21

20

19

18

17

16

26

25

24

15

14

13

12

11

23

22

10

3

4

9

1

2

8

7

6

5

F11

1 2

29

4

3

1

2

7

6

5

10 11 12 13 14 15

25

24

16

30

9

8

17 18 19

20
28

21 22 23

32

31

26 27

33

34 35

B220

18

19

6

7

4

3
5

2

1

12

11

10

9

8

40

36 39

38

37

34

33

35

32

28 31

30

29

23

22

21

20

26

25

24

27

17

16

15

14

13

4

3

B220

15A

16

15

8

7

4

14

13

11

12

10

9

2

1

3

6

5

B143

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

F37

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

B144

3
8

2
6

7

1
5

4
9

31

30

32

29

34

33

21

20

19

18

17

16

28

27

26

15

14

13

12

11

25

23

22

24

10

3

4

9

1

2

8

7

6

5

E40

2

6

5

4

3

1

E41

2

1

54

52 53

50 51

48 49

46 47

45

44

42 43

40 41

38 39

36 37

34 35

33

32

31

30

29

28

27

26

25

24

23

22

21

20

11

10

9

19

18

17

16

8

7

6

5

15

14

13

12

4

3

2

1

B21

E

E

E

ECM

SBF-7

FUSE

(RELAY BLOCK)

MAIN SBF

MAIN RELAY

SECONDARY

AIR COMBINATION

VALVE RELAY 2

SECONDARY

AIR PUMP

RELAY

SECONDARY

AIR COMBINATION

VALVE RH

SECONDARY

AIR COMBINATION

VALVE LH

(WITH BUILT-IN

PRESSURE SENSOR)

SECONDARY

AIR COMBINATION

VALVE RELAY 1

SECONDARY

AIR PUMP

MAIN FUSE BOX

(M/B)

RELAY HOLDER

BATTERY

EN(H4DOTC)(diag)-449

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

2

CHECK HARNESS BETWEEN FUSE BOX
AND SECONDARY AIR COMBINATION
VALVE RH CONNECTOR.
1) Remove the secondary air combination
valve fuse (10 A) from the fuse box.
2) Disconnect the connector from the second-
ary air combination valve RH.
3) Measure the resistance between the sec-
ondary air combination valve fuse and second-
ary air combination valve RH connector, and
chassis ground.

Connector & terminal

Models without SI-DRIVE

(F9) No. 5 — Chassis ground:
(E41) No. 6 — Chassis ground:

Models with SI-DRIVE

(F9) No. 5 — Chassis ground:
(E41) No. 2 — Chassis ground:

Is the resistance 1 MΩ or
more?

Replace the fuse
with a new part,
and connect the
secondary air com-
bination valve RH
connector.
Go to step

3.

Repair the short
circuit to ground in
harness between
the fuse box and
the secondary air
combination valve
RH connector.

3

CHECK SECONDARY AIR COMBINATION
VALVE RH OPERATION.
1) Connect the delivery (test) mode connector.
2) Turn the ignition switch to ON.
3) Perform operation check for the secondary
air combination valve RH using the Subaru
Select Monitor.
NOTE:

Refer to “Compulsory Valve Operation Check
Mode” for more operation procedures. <Ref. to
EN(H4DOTC)(diag)-64, Compulsory Valve Op-
eration Check Mode.>

Does the secondary air combi-
nation valve RH repeatedly
switch to ON and OFF?

Go to step

4.

Go to step

6.

4

CHECK DUCT BETWEEN SECONDARY AIR
PUMP AND SECONDARY AIR COMBINA-
TION VALVE RH.
Check the duct between the secondary air
pump and secondary air combination valve RH.

Is there damage, clog or dis-
connection of the duct?

Replace, clean or
connect the duct.

Go to step

5.

5

CHECK PIPE BETWEEN SECONDARY AIR
COMBINATION VALVE RH AND CYLINDER
HEAD.
Check the pipe between the secondary air com-
bination valve RH and cylinder head.

Is there damage, clog or dis-
connection of the pipe?

Replace, clean or
connect the pipe.

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 poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.

Step

Check

Yes

No

EN(H4DOTC)(diag)-450

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

6

CHECK POWER SUPPLY TO SECONDARY
AIR COMBINATION VALVE RH.
1) Disconnect the connector from the second-
ary air combination valve RH.
2) In the condition of step 3, measure the volt-
age between secondary air combination valve
RH connector and chassis ground.

Connector & terminal

Models without SI-DRIVE

(E41) No. 6 (+) — Chassis ground (–):

Models with SI-DRIVE

(E41) No. 2 (+) — Chassis ground (–):

Does the voltage repeatedly
change between 10 V and 0 V?

Replace the sec-
ondary air combi-
nation valve RH.
<Ref. to EC(STI)-
29, Secondary Air
Combination
Valve.> <Ref. to
EC(w/o STI)-30,
Secondary Air
Combination
Valve.>

Go to step

7.

7

CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE RH AND CHAS-
SIS GROUND.
Measure the resistance between the secondary
air combination valve RH connector and chas-
sis ground.

Connector & terminal

Models without SI-DRIVE

(E41) No. 4 — Chassis ground:

Models with SI-DRIVE

(E41) No. 1 — Chassis ground:

Is the resistance less than 5 Ω? • Models without

SI-DRIVE: Go to
step

8.

• Models with SI-
DRIVE: Go to step
14.

Repair the open
circuit in harness
between second-
ary air combination
valve RH connec-
tor and chassis
ground.

8

CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE RELAY 1 AND
SECONDARY AIR COMBINATION VALVE
RH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the secondary air combination
valve relay 1 from the relay box.
3) Measure the resistance of the harness
between secondary air combination valve relay
1 connector and secondary air combination
valve RH connector.

Connector & terminal

(F9) No. 3 — (E41) No. 6:

Is the resistance less than 1 Ω? Go to step

9.

Repair the open
circuit in harness
between second-
ary air combination
valve relay 1 and
secondary air com-
bination valve RH
connector.

9

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 1.
1) Connect the battery to terminals No. 1 and
No. 2 of the secondary air combination valve
relay 1.
2) Measure the resistance between the sec-
ondary air combination valve relay 1 terminals.

Terminals

No. 3 — No. 4:

Is the resistance less than 1 Ω? Go to step

10.

Replace the sec-
ondary air combina-
tion valve relay 1.
<Ref. to
EN(H4DOTC)(diag)
-9, Electrical Com-
ponent Location.>

10

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 1.
Measure the resistance between the secondary
air combination valve relay 1 terminals with the
battery disconnected.

Terminals

No. 3 — No. 4:

Is the resistance 1 MΩ or
more?

Go to step

11.

Replace the sec-
ondary air combina-
tion valve relay 1.
<Ref. to
EN(H4DOTC)(diag)
-9, Electrical Com-
ponent Location.>

Step

Check

Yes

No

EN(H4DOTC)(diag)-451

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

11

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 1 POWER SUPPLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between the second-
ary air combination valve relay 1 connector and
chassis ground.

Connector & terminal

(F9) No. 4 (+) — Chassis ground (–):
(F9) No. 1 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

12.

Repair the open or
ground short circuit
of power supply
circuit.

12

CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 1 CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the ECM connector.
3) Measure the resistance of harness between
ECM connector and secondary air combination
valve relay 1 connector.

Connector & terminal

(B135) No. 8 — (F9) No. 2:

Is the resistance less than 1 Ω? Go to step

13.

Repair the harness
and connector.
NOTE:

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

connector

and secondary air
combination valve
relay 1 connector
• Poor contact of
coupling connector

13

CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 1 CONNECTOR.
Measure the resistance between the secondary
air combination valve relay 1 connector and
chassis ground.

Connector & terminal

(F9) No. 2 — Chassis ground:

Is the resistance 1 MΩ or
more?

Repair the poor
contact of ECM
connector.

Repair the short
circuit to ground in
harness between
ECM connector
and secondary air
combination valve
relay 1 connector.

14

CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE RELAY 2 AND
SECONDARY AIR COMBINATION VALVE
RH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the secondary air combination
valve relay 2 from the relay box.
3) Measure the resistance of the harness
between secondary air combination valve relay
2 connector and secondary air combination
valve RH connector.

Connector & terminal

(F9) No. 8 — (E41) No. 2:

Is the resistance less than 1 Ω? Go to step

15.

Repair the open
circuit in harness
between second-
ary air combination
valve relay 2 and
secondary air com-
bination valve RH
connector.

15

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 2.
1) Connect the battery to terminals No. 9 and
No. 10 of the secondary air combination valve
relay 2.
2) Measure the resistance between the sec-
ondary air combination valve relay 2 terminals.

Terminals

No. 7 — No. 8:

Is the resistance less than 1 Ω? Go to step

16.

Replace the sec-
ondary air combina-
tion valve relay 2.
<Ref. to
EN(H4DOTC)(diag)
-9, Electrical Com-
ponent Location.>

16

CHECK SECONDARY AIR COMBINATION
VALVE RELAY 2.
Measure the resistance between the secondary
air combination valve relay 2 terminals with the
battery disconnected.

Terminals

No. 7 — No. 8:

Is the resistance 1 MΩ or
more?

Go to step

17.

Replace the sec-
ondary air combina-
tion valve relay 2.
<Ref. to
EN(H4DOTC)(diag)
-9, Electrical Com-
ponent Location.>

Step

Check

Yes

No