Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 251

EN(H4DOTC)(diag)-228

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 PUMP FUSE.
Check if the secondary air pump fuse (60 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)-229

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

2

CHECK HARNESS BETWEEN FUSE BOX
AND SECONDARY AIR PUMP CONNECTOR.
1) Remove the secondary air pump fuse from
the fuse box.
2) Disconnect the secondary air pump connec-
tor.
3) Measure the resistance between the sec-
ondary air pump fuse and secondary air pump
connector, and chassis ground.

Connector & terminal

(F9) No. 16 — Chassis ground:
(F11) No. 2 — Chassis ground:

Is the resistance 1 MΩ or
more?

Replace the fuse
with a new part,
and connect the
secondary air
pump connector.
Go to step

3.

Repair ground
short of the har-
ness between the
fuse box and the
secondary air
pump connector.

3

CHECK SECONDARY AIR PUMP OPERA-
TION.
CAUTION:

Try your best to complete the confirmation
process of this inspection in one try. This in-
spection will put a heavy workload on the
secondary air pump, so the continuous op-
eration may cause damage to the pump. Do
not operate the pump continuously for more
than three times. If you need to operate the
pump further, turn the ignition switch to
OFF and wait for at least two hours.
1) Connect the delivery (test) mode connector.
2) Turn the ignition switch to ON.
3) Perform operation check for the secondary
air pump using the Subaru Select Monitor.
NOTE:

• The compulsory operation using the Subaru
Select Monitor is performed only for 10 seconds
in order to protect the secondary air pump.
When you want to operate the pump again, dis-
connect the ground cable from battery, wait at
least one minute, and perform the clear memo-
ry operation of ECM. Then, perform the forced
operation using the Subaru Select Monitor.
• Refer to “Compulsory Valve Operation Check
Mode” for detailed procedures. <Ref. to
EN(H4DOTC)(diag)-64, Compulsory Valve Op-
eration Check Mode.>

Does the secondary air pump
operate?

Go to step

4.

Go to step

5.

4

CHECK DUCT BETWEEN SECONDARY AIR
PUMP AND COMBINATION VALVE.
Check the duct between secondary air pump
and combination valve.

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

Replace, clean or
connect the duct.

Replace the sec-
ondary air combi-
nation valve LH
(models with SI-
DRIVE) or RH
(models without
SI-DRIVE). <Ref.
to EC(STI)-29,
Secondary Air
Combination
Valve.> <Ref. to
EC(w/o STI)-30,
Secondary Air
Combination
Valve.>

Step

Check

Yes

No

EN(H4DOTC)(diag)-230

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

5

CHECK POWER SUPPLY TO SECONDARY
AIR PUMP.
1) Turn the ignition switch to OFF.
2) Disconnect the battery negative terminal,
wait for 1 minute, and connect it again.
3) Disconnect the secondary air pump connec-
tor.
4) Connect the delivery (test) mode connector.
5) Turn the ignition switch to ON.
6) Using the Subaru Select Monitor, measure
the voltage between the secondary air pump
connector and chassis ground while the sec-
ondary air pump is operating.
NOTE:

• The compulsory operation using the Subaru
Select Monitor is performed only for 10 seconds
in order to protect the secondary air pump.
When you want to operate the pump again, dis-
connect the ground cable from battery, wait at
least one minute, and perform the clear memo-
ry operation of ECM. Then, perform the forced
operation using the Subaru Select Monitor.
• Refer to “Compulsory Valve Operation Check
Mode” for detailed procedures. <Ref. to
EN(H4DOTC)(diag)-64, Compulsory Valve Op-
eration Check Mode.>

Connector & terminal

(F11) No. 2 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Replace the sec-
ondary air pump.
<Ref. to EC(STI)-
27, Secondary Air
Pump.> <Ref. to
EC(w/o STI)-29,
Secondary Air
Pump.>

Go to step

6.

6

CHECK HARNESS BETWEEN SECONDARY
AIR PUMP RELAY AND SECONDARY AIR
PUMP CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the secondary air pump relay.
3) Measure the resistance of harness between
secondary air pump relay connector and sec-
ondary air pump connector.

Connector & terminal

(F9) No. 11 — (F11) No. 2:

Is the resistance less than 1 Ω? Go to step

7.

Repair the open
circuit in harness
between second-
ary air pump relay
connector and sec-
ondary air pump
connector.

7

CHECK HARNESS BETWEEN SECONDARY
AIR PUMP CONNECTOR AND CHASSIS
GROUND.
Measure the resistance of the harness between
secondary air pump connector and chassis
ground.

Connector & terminal

(F11) No. 1 — Chassis ground:

Is the resistance less than 5 Ω? Go to step

8.

Repair the open
circuit of the har-
ness between sec-
ondary air pump
connector and
chassis ground.

8

CHECK SECONDARY AIR PUMP RELAY.
1) Connect the battery to terminals No. 12 and
No. 13 of the secondary air pump relay.
2) Measure the resistance between secondary
air pump relay terminals.

Terminals

No. 14 — No. 11:

Is the resistance less than 1 Ω? Go to step

9.

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

Step

Check

Yes

No

EN(H4DOTC)(diag)-231

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

9

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

Connector & terminal

(F9) No. 14 (+) — Chassis ground (–):
(F9) No. 12 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

10.

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

10

CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR PUMP RELAY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the ECM connector.
3) Measure the resistance of harness between
ECM connector and secondary air pump relay
connector.

Connector & terminal

(B135) No. 27 — (F9) No. 13:

Is the resistance less than 1 Ω? Repair the poor

contact of ECM
connector.

Repair the harness
and connector.
NOTE:

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

connector

and secondary air
pump relay con-
nector
• Poor contact of
coupling connector

Step

Check

Yes

No