Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 223

EN(H4DOTC)(diag)-116

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

M: DTC P0038 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 2)

DTC DETECTING CONDITION:

• Detected when 2 consecutive driving cycles with fault occur.

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-30, DTC P0038 HO2S HEATER CONTROL CIRCUIT

HIGH (BANK 1 SENSOR 2), 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:

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

System.>

ECM

6

4 5

3

2

1

*

2

1

B220

15A

9

10

11
12

B220

*

*

1 2
3 4

D1

36

A4

40

34

35

B21

E2

D3

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-08722

E

E

SBF-5

BATTERY

: TERMINAL No. OPTIONAL ARRANGEMENT

REAR

OXYGEN SENSOR

A/F, OXYGEN SENSOR

RELAY

FUSE

(RELAY BLOCK)

EN(H4DOTC)(diag)-117

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 HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the voltage between ECM connec-
tor and chassis ground.

Connector & terminal

(B135) No. 6 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Repair the short
circuit to power in
the harness
between ECM con-
nector and rear
oxygen sensor
connector.

Go to step

2.

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)-118

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

2

CHECK GROUND CIRCUIT FOR ECM.
1) Disconnect the connector from ECM.
2) Measure the resistance between ECM con-
nector and chassis ground.

Connector & terminal

(B134) No. 3 — Chassis ground:
(B134) No. 4 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 3 — Chassis ground:

Is the resistance less than 5 Ω? Repair the poor

contact of ECM
connector.

Repair the harness
and connector.
NOTE:

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

connector

and engine ground
• Poor contact of
coupling connector

Step

Check

Yes

No

EN(H4DOTC)(diag)-119

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

N: DTC P0068 MAP/MAF - THROTTLE POSITION CORRELATION

DTC DETECTING CONDITION:

• Detected when two consecutive driving cycles with fault occur.

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-32, DTC P0068 MAP/MAF - THROTTLE POSITION

CORRELATION, 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.>.

Step

Check

Yes

No

1

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

2.

2

CHECK MANIFOLD ABSOLUTE PRESSURE
SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the value of «Mani. Absolute Pres-
sure» using the Subaru Select Monitor or a gen-
eral scan tool.
NOTE:

• Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-40, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
“General Scan Tool Instruction Manual”.

Is the value in «Mani. Absolute
Pressure» 73.3 — 106.6 kPa
(550 — 800 mmHg, 21.65 —
31.50 inHg) when the ignition is
turned ON, and 20.0 — 46.7
kPa (150 — 350 mmHg, 5.91 —
13.78 inHg) during idling?

Go to step

3.

Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(STI)-43,
Manifold Absolute
Pressure Sen-
sor.> <Ref. to
FU(w/o STI)-43,
Manifold Absolute
Pressure Sensor.>

3

CHECK THROTTLE OPENING ANGLE.
Using the Subaru Select Monitor or a general
scan tool, read the value in «Throttle Opening
Angle».
NOTE:

• Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-40, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
“General Scan Tool Instruction Manual”.

Is the value in «Throttle Open-
ing Angle» with the throttle fully
closed less than 5%?

Go to step

4.

Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.> <Ref. to
FU(w/o STI)-15,
Throttle Body.>

4

CHECK THROTTLE OPENING ANGLE.

Is the value in «Throttle Open-
ing Angle» with the throttle fully
open 85% or more?

Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(STI)-43,
Manifold Absolute
Pressure Sen-
sor.> <Ref. to
FU(w/o STI)-43,
Manifold Absolute
Pressure Sensor.>

Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.> <Ref. to
FU(w/o STI)-15,
Throttle Body.>