Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 225

EN(H4DOTC)(diag)-124

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Q: DTC P0103 MASS OR VOLUME AIR FLOW CIRCUIT HIGH INPUT

DTC DETECTING CONDITION:

• Immediately at fault recognition

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-38, DTC P0103 MASS OR VOLUME AIR FLOW CIR-

CUIT HIGH INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>

TROUBLE SYMPTOM:

• Improper idling

• Engine stalls.

• Poor driving performance
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

EN-08725

B135

B:

B3

B83

3

B3

B135

B:

B136

C:

1 2 3 4 5

*

*

4

1

5

2

C11

C31

C22

B30

C10

*

B220

24

23

22

21

15A

B220

3

4

B136

C:

B83

6

4 5

3

2

1

35

27

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

26

33 34

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

35

34

33

32

31

30

29

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

SBF-7

E

FUSE

(RELAY BLOCK)

MAIN RELAY

: TERMINAL No. OPTIONAL

ARRANGEMENT

MASS AIR FLOW &

INTAKE AIR

TEMPERATURE SENSOR

BATTERY

EN(H4DOTC)(diag)-125

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «Air Flow Sensor Volt-
age» using Subaru Select Monitor.
NOTE:

For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-40, Subaru Select Moni-
tor.>

Is the value of «Air Flow Sensor
Voltage» 5 V or more?

Go to step

2.

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.

2

CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the mass
air flow and intake air temperature sensor.
3) Start the engine.
4) Read the value of «Air Flow Sensor Volt-
age» using Subaru Select Monitor.
NOTE:

For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-40, Subaru Select Moni-
tor.>

Is the value of «Air Flow Sensor
Voltage» 5 V or more?

Repair the short
circuit of harness
to power supply
between ECM con-
nector and the
mass air flow and
intake air tempera-
ture sensor con-
nector.

Go to step

3.

3

CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness between
mass air flow and intake air temperature sensor
connector and engine ground.

Connector & terminal

(B3) No. 4 — Engine ground:

Is the resistance less than 5 Ω? Go to step

4.

Repair the harness
and connector.
NOTE:

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

connector

and the mass air
flow and intake air
temperature sen-
sor connector
• Poor contact of
ECM connector

4

CHECK FOR POOR CONTACT.
Check for poor contact of mass air flow and
intake air temperature sensor connector.

Is there poor contact of mass
air flow and intake air tempera-
ture sensor connector?

Repair the poor
contact of mass air
flow and intake air
temperature sen-
sor connector.

Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-42, Mass
Air Flow and Intake
Air Temperature
Sensor.> <Ref. to
FU(w/o STI)-42,
Mass Air Flow and
Intake Air Temper-
ature Sensor.>

EN(H4DOTC)(diag)-126

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

R: DTC P0107 MANIFOLD ABSOLUTE PRESSURE/BAROMETRIC PRESSURE

CIRCUIT LOW INPUT

DTC DETECTING CONDITION:

• Immediately at fault recognition

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-40, DTC P0107 MANIFOLD ABSOLUTE PRESSURE/

BAROMETRIC PRESSURE CIRCUIT LOW INPUT, 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

EN-08724

6

2

8

23

1

3

2

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

B134

A:

A29

D20

A19

2

3

1

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

3

2

1

B137

D:

B134

A:

B21

E21

E21

E2

B21

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

ES

SI

SI

ES

: WITHOUT SI-DRIVE

: WITH SI-DRIVE

MANIFOLD

ABSOLUTE

PRESSURE

SENSOR

EN(H4DOTC)(diag)-127

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK CURRENT DATA.
1) Start the engine.
2) 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 operation manual.

Is the value of «Mani. Absolute
Pressure» less than 13.3 kPa
(100 mmHg, 3.94 inHg)?

Go to step

2.

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.

2

CHECK POWER SUPPLY OF MANIFOLD
ABSOLUTE PRESSURE SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from manifold
absolute pressure sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between manifold
absolute pressure sensor connector and
engine ground.

Connector & terminal

(E21) No. 3 (+) — Engine ground (–):

Is the voltage 4.5 V or more?

Go to step

3.

Repair the harness
and connector.
NOTE:

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

connector

and manifold abso-
lute pressure sen-
sor connector
• Poor contact of
ECM connector
• Poor contact of
coupling connector

3

CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness between
ECM connector and manifold absolute pres-
sure sensor connector.

Connector & terminal

Models without SI-DRIVE

(B137) No. 20 — (E21) No. 2:

Models with SI-DRIVE

(B137) No. 20 — (E21) No. 1:

Is the resistance less than 1 Ω? Go to step

4.

Repair the harness
and connector.
NOTE:

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

connector

and manifold abso-
lute pressure sen-
sor connector
• Poor contact of
coupling connector

4

CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.

Connector & terminal

(B137) No. 20 — Chassis ground:

Is the resistance 1 MΩ or
more?

Go to step

5.

Repair short circuit
to ground in har-
ness between
ECM connector
and manifold abso-
lute pressure sen-
sor connector.