Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 285

EN(H4DOTC)(diag)-364

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.>

ECM

B138

6

4 5

3

2

1

1

2

3

4

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

2

1

B220

15A

9

10

11
12

B220

D:

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

C: B136

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

*

*

*

B138

D1

36

D3

A4

40

34

35

B21

E2

A6

A3

A:

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

D: B137

C: B136

A:

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

B134

B379

B21

B379

4

2

3

1

B134

C9

C19

C1

8

C6

C5

EN-08721

SBF-5

E

E

FRONT OXYGEN (A/F)

SENSOR

BATTERY

: TERMINAL No. OPTIONAL ARRANGEMENT

A/F, OXYGEN SENSOR

RELAY

FUSE

(RELAY BLOCK)

EN(H4DOTC)(diag)-365

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?

Check DTC using
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(H4DOTC)(diag)
-87, List of Diagnos-
tic Trouble Code
(DTC).>

Go to step

2.

2

CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.

Has water entered the connec-
tor?

Completely
remove any water
inside.

Go to step

3.

ECM

6

4 5

3

2

1

*

2

1

B220

15A

9

10

11
12

B220

*

*

1 2
3 4

D1

36

D3 A4

40

34

35

B21

E2

A6

A3

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

B134

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

A:

D: B137

C: B136

B: B135

A:

T6

B134

C9

B30

C20

B6

*

*

B21

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

4

1

3

4

1

3

B19

T5

22

T5

B19

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

B135

B:

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

B136

C:

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

35

D: B137

B19

T6

B83

B138

B138

B83

EN-08723

SBF-5

E

E

BATTERY

: TERMINAL No. OPTIONAL ARRANGEMENT

REAR

OXYGEN SENSOR

A/F, OXYGEN SENSOR

RELAY

FUSE

(RELAY BLOCK)

EN(H4DOTC)(diag)-366

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

3

CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
3) Measure the resistance of harness between
ECM connector and front oxygen (A/F) sensor
connector.

Connector & terminal

Models without SI-DRIVE

(B136) No. 19 — (E22) No. 1:
(B136) No. 18 — (E22) No. 3:

Models with SI-DRIVE

(B136) No. 19 — (B379) No. 4:
(B136) No. 18 — (B379) No. 3:

Is the resistance less than 1 Ω? Go to step

4.

Repair the open
circuit of harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.

4

CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance between ECM connec-
tor and chassis ground.

Connector & terminal

(B136) No. 19 — Chassis ground:
(B136) No. 18 — 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 front oxygen
(A/F) sensor con-
nector.

5

CHECK OUTPUT SIGNAL FOR ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between front oxygen
(A/F) sensor connector and chassis ground.

Connector & terminal

Models without SI-DRIVE

(E22) No. 1 (+) — Chassis ground (–):

Models with SI-DRIVE

(B379) No. 4 (+) — Chassis ground (–):

Is the voltage 4.5 V or more?

Go to step

7.

Go to step

6.

6

CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/F)
sensor connector and chassis ground.

Connector & terminal

Models without SI-DRIVE

(E22) No. 3 (+) — Chassis ground (–):

Models with SI-DRIVE

(B379) No. 3 (+) — Chassis ground (–):

Is the voltage 4.95 V or more? Go to step

7.

Go to step

8.

7

CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/F)
sensor connector and chassis ground.

Connector & terminal

Models without SI-DRIVE

(E22) No. 3 (+) — Chassis ground (–):
(E22) No. 1 (+) — Chassis ground (–):

Models with SI-DRIVE

(B379) No. 3 (+) — Chassis ground (–):
(B379) No. 4 (+) — Chassis ground (–):

Is the voltage 8 V or more?

Repair the short
circuit to power in
the harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
After repair,
replace the ECM.
<Ref. to FU(STI)-
59, Engine Control
Module (ECM).>
<Ref. to FU(w/o
STI)-57, Engine
Control Module
(ECM).>

Repair the poor
contact of ECM
connector.

8

CHECK EXHAUST SYSTEM.

Are there holes or loose bolts
on exhaust system?

Repair the exhaust
system.

Go to step

9.

Step

Check

Yes

No

EN(H4DOTC)(diag)-367

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

9

CHECK AIR INTAKE SYSTEM.

Are there holes, loose bolts or
disconnection of hose on air
intake system?

Repair the air
intake system.

Go to step

10.

10

CHECK FUEL PRESSURE.
WARNING:

Place “NO OPEN FLAMES” signs near the
working area.
CAUTION:

Be careful not to spill fuel.
1) Connect the front oxygen (A/F) sensor con-
nector.
2) Measure the fuel pressure while discon-
necting pressure regulator vacuum hose from
intake manifold. <Ref. to ME(STI)-25, INSPEC-
TION, Fuel Pressure.> <Ref. to ME(w/o STI)-
24, INSPECTION, Fuel Pressure.>
CAUTION:

Release fuel pressure before removing the
fuel pressure gauge.
NOTE:

If fuel pressure does not increase, squeeze the
fuel return hose 2 to 3 times, then measure fuel
pressure again.

Is the measured value 284 —
314 kPa (2.9 — 3.2 kgf/cm

2

, 41

— 46 psi)?

Go to step

11.

Check the fuel
pump and fuel
delivery line.
• Models without
SI-DRIVE <Ref. to
FU(w/o STI)-79,
INSPECTION,
Fuel Pump.> <Ref.
to FU(w/o STI)-93,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
• Models with SI-
DRIVE <Ref. to
FU(STI)-81,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-97,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>

11

CHECK FUEL PRESSURE.
After connecting the pressure regulator vacuum
hose, measure fuel pressure. <Ref. to ME(STI)-
25, INSPECTION, Fuel Pressure.> <Ref. to
ME(w/o STI)-24, INSPECTION, Fuel Pres-
sure.>
CAUTION:

Release fuel pressure before removing the
fuel pressure gauge.
NOTE:

• If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure fuel
pressure again.
• If the measured value at this step is out of
specification, check or replace pressure regula-
tor and pressure regulator vacuum hose.

Is the measured value 230 —
260 kPa (2.4 — 2.7 kgf/cm

2

, 33

— 38 psi)?

Go to step

12.

Check the fuel
pump and fuel
delivery line.
• Models without
SI-DRIVE <Ref. to
FU(w/o STI)-79,
INSPECTION,
Fuel Pump.> <Ref.
to FU(w/o STI)-93,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
• Models with SI-
DRIVE <Ref. to
FU(STI)-81,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-97,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>

Step

Check

Yes

No