Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Service 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?
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
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-
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, with SI-DRIVE <Ref. to WI-48, WITH SI-DRIVE, WIRING DIAGRAM, Engine
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?
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
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