Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 237

EN(H4DOTC)(diag)-172

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

4

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 kg/cm

2

, 33

— 38 psi)?

Go to step

5.

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.>

5

CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm up completely.
2) Read the value of «Coolant Temp.» using
the Subaru Select Monitor or a general 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 «Coolant
Temp.» 75°C (167°F) or more?

Go to step

6.

Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-34,
Engine Coolant
Temperature Sen-
sor.> <Ref. to
FU(w/o STI)-34,
Engine Coolant
Temperature Sen-
sor.>

6

CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE 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 «Mass Air Flow» using
the Subaru Select Monitor or a general 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 «Mass Air Flow»
2.0 — 5.0 g/s (0.26 — 0.66 lb/m)?

Go to step

7.

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.>

Step

Check

Yes

No

EN(H4DOTC)(diag)-173

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

7

CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE 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) Open the front hood.
6) Measure the ambient temperature.
7) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general 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.

Subtract ambient temperature
from «Intake Air Temp.». Is the
obtained value –10 — 50°C (–18
— 90°F)?

Repair the poor
contact of ECM
connector.

Check the mass air
flow and intake air
temperature sen-
sor. <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.>

Step

Check

Yes

No

EN(H4DOTC)(diag)-174

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

AU:DTC P0201 INJECTOR #1

DTC DETECTING CONDITION:

• Immediately at fault recognition

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-100, DTC P0201 INJECTOR #1, Diagnostic Trouble

Code (DTC) Detecting Criteria.>

TROUBLE SYMPTOM:

• Improper idling

• 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-08718

#4

2

1

#3

2

1

#2

2

1

B21

#1

2

1

4

8

54

53

52

51

10

11

12

13

1 2

B21

E5

E5

E2

E6

E6

E16

E16

E17

E17

B134

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

B220

24

23

22

15A

B220

3

4

21

B134

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

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

E

SBF-7

MAIN RELAY

FUSE

(RELAY BLOCK)

FUEL INJECTOR

BATTERY

EN(H4DOTC)(diag)-175

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK POWER SUPPLY TO FUEL INJEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector.
3) Turn the ignition switch to ON.
4) Measure the voltage between fuel injector
connector and the engine ground.

Connector & terminal

DTC P0201; (E5) No. 1 (+) — Engine
ground (–):
DTC P0202; (E16) No. 1 (+) — Engine
ground (–):
DTC P0203; (E6) No. 1 (+) — Engine
ground (–):
DTC P0204; (E17) No. 1 (+) — Engine
ground (–):

Is the voltage 10 V or more?

Go to step

2.

Repair the harness
and connector.
NOTE:

In this case, repair
the following item:
• Open circuit in
harness between
main relay and fuel
injector connector
• Poor contact of
main relay connec-
tor
• Poor contact of
coupling connector

2

CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between fuel injec-
tor connector and engine ground.

Connector & terminal

DTC P0201; (E5) No. 2 — Engine ground:
DTC P0202; (E16) No. 2 — Engine
ground:
DTC P0203; (E6) No. 2 — Engine ground:
DTC P0204; (E17) No. 2 — Engine
ground:

Is the resistance 1 MΩ or
more?

Go to step

3.

Repair the short
circuit to ground in
harness between
ECM connector
and fuel injector
connector.

3

CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
Measure the resistance of harness between
ECM connector and fuel injector connector.

Connector & terminal

DTC P0201; (B134) No. 10 — (E5) No. 2:
DTC P0202; (B134) No. 11 — (E16) No. 2:
DTC P0203; (B134) No. 12 — (E6) No. 2:
DTC P0204; (B134) No. 13 — (E17) No. 2:

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 in
harness between
ECM

connector

and fuel injector
connector
• Poor contact of
coupling connector

4

CHECK FUEL INJECTOR.
Measure the resistance between fuel injector
terminals on the corresponding cylinder.

Terminals

No. 1 — No. 2:

Is the resistance 5 — 20 Ω?

Go to step

5.

Replace the fuel
injector. <Ref. to
FU(STI)-45, Fuel
Injector.> <Ref. to
FU(w/o STI)-45,
Fuel Injector.>

5

CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.

Is there poor contact of ECM
connector?

Repair the poor
contact of ECM
connector.

Go to step

6.