Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 243

EN(H4DOTC)(diag)-196

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

13

CHECK CAUSE OF MISFIRE.

Was the cause of misfire identi-
fied when the engine is run-
ning?

Finish diagnostics
operation, if the
engine has no
abnormality.

Repair the poor
contact of connec-
tor.
NOTE:

In this case, repair
the following item:
• Poor contact of
ignition coil con-
nector
• Poor contact of
fuel injector con-
nector on faulty
cylinders
• Poor contact of
ECM connector
• Poor contact of
coupling connector

14

CHECK AIR INTAKE SYSTEM.

Is there any fault in air intake
system?

Repair the air
intake system.
NOTE:

Check the follow-
ing items.
• Are there air
leaks or air suction
caused by loose or
dislocated

nuts

and bolts?
• Are there cracks
or any disconnec-
tion of hoses?

Go to step

15.

15

CHECK ALL CYLINDERS.

Is there a fault in any cylinder? Repair or replace

the faulty part of
the faulty cylinder.
NOTE:

Check the follow-
ing items.
• Spark plug
• Fuel injector
• Ignition coil
• Compression ra-
tio
• Skipping timing
belt teeth

Go to DTC P0171.
<Ref. to
EN(H4DOTC)(diag)
-170, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>

Step

Check

Yes

No

EN(H4DOTC)(diag)-197

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BF:DTC P0301 CYLINDER 1 MISFIRE DETECTED

NOTE:

For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(H4DOTC)(diag)-198, DTC P0304 CYLIN-

DER 4 MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BG:DTC P0302 CYLINDER 2 MISFIRE DETECTED

NOTE:

For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(H4DOTC)(diag)-198, DTC P0304 CYLIN-

DER 4 MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

BH:DTC P0303 CYLINDER 3 MISFIRE DETECTED

NOTE:

For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(H4DOTC)(diag)-198, DTC P0304 CYLIN-

DER 4 MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

EN(H4DOTC)(diag)-198

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BI: DTC P0304 CYLINDER 4 MISFIRE DETECTED

DTC DETECTING CONDITION:

• Detected when 2 consecutive driving cycles with fault occur.

• Immediately at fault recognition (A misfire which could damage catalyst occurs.)

• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-123, DTC P0304 CYLINDER 4 MISFIRE DETECTED,

Diagnostic Trouble Code (DTC) Detecting Criteria.>

TROUBLE SYMPTOM:

• Engine stalls.

• Improper idling

• Rough driving
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.>.

EN(H4DOTC)(diag)-199

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

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.>

Step

Check

Yes

No

1

CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM and
chassis ground on faulty cylinders.

Connector & terminal

#1 (B134) No. 10 (+) — Chassis ground (–):
#2 (B134) No. 11 (+) — Chassis ground (–):
#3 (B134) No. 12 (+) — Chassis ground (–):
#4 (B134) No. 13 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

6.

Go to step

2.

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