Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 244

EN(H4DOTC)(diag)-200

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

2

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

Connector & terminal

#1 (E5) No. 2 — Engine ground:
#2 (E16) No. 2 — Engine ground:
#3 (E6) No. 2 — Engine ground:
#4 (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 and fuel injector connector on faulty cylin-
ders.

Connector & terminal

#1 (B134) No. 10 — (E5) No. 2:
#2 (B134) No. 11 — (E16) No. 2:
#3 (B134) No. 12 — (E6) No. 2:
#4 (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 faulty cylinder.

Terminals

No. 1 — No. 2:

Is the resistance 5 — 20 Ω?

Go to step

5.

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

5

CHECK POWER SUPPLY LINE.
1) Turn the ignition switch to ON.
2) Measure the voltage between fuel injector
connector of faulty cylinders and engine
ground.

Connector & terminal

#1 (E5) No. 1 (+) — Engine ground (–):
#2 (E16) No. 1 (+) — Engine ground (–):
#3 (E6) No. 1 (+) — Engine ground (–):
#4 (E17) No. 1 (+) — Engine ground (–):

Is the voltage 10 V or more?

Repair the poor
contact of all con-
nectors in fuel
injector circuit.

Repair the harness
and connector.
NOTE:

In this case, repair
the following item:
• Open circuit in
harness between
the main relay con-
nector and fuel in-
jector connector on
faulty cylinders
• Poor contact of
coupling connector
• Poor contact of
main relay connec-
tor

Step

Check

Yes

No

EN(H4DOTC)(diag)-201

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

6

CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector
on faulty cylinders.
3) Turn the ignition switch to ON.
4) 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?

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

Go to step

7.

7

CHECK FUEL INJECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between fuel injec-
tor terminals on faulty cylinder.

Terminals

No. 1 — No. 2:

Is the resistance 5 — 20 Ω?

Go to step

8.

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

8

CHECK INSTALLATION OF CAMSHAFT PO-
SITION SENSOR/CRANKSHAFT POSITION
SENSOR.

Is the camshaft position sensor
or crankshaft position sensor
loosely installed?

Tighten the cam-
shaft position sen-
sor or crankshaft
position sensor.
<Ref. to FU(STI)-
37, Camshaft Posi-
tion Sensor.>
<Ref. to FU(STI)-
35, Crankshaft
Position Sensor.>
<Ref. to FU(w/o
STI)-37, Camshaft
Position Sensor.>
<Ref. to FU(w/o
STI)-35, Crank-
shaft Position Sen-
sor.>

Go to step

9.

9

CHECK CRANK SPROCKET.
Remove the timing belt cover.

Is the crank sprocket rusted or
does it have broken teeth?

Replace the crank
sprocket. <Ref. to
ME(STI)-60, Crank
Sprocket.> <Ref. to
ME(w/o STI)-58,
Crank Sprocket.>

Go to step

10.

10

CHECK INSTALLATION CONDITION OF
TIMING BELT.
Turn the crankshaft, and align alignment mark
on crank sprocket with alignment mark on cylin-
der block.
ST 499987500

CRANKSHAFT
SOCKET

Is the timing belt dislocated
from its proper position?

Repair the installa-
tion condition of
timing belt. <Ref.
to ME(STI)-50,
Timing Belt.> <Ref.
to ME(w/o STI)-48,
Timing Belt.>

Go to step

11.

11

CHECK FUEL LEVEL.

Is the fuel meter indication
higher than the “Lower” level?

Go to step

12.

Refill the fuel so
that the fuel meter
indication is higher
than the “Lower”
level, and proceed
to the next step.
Go to step

12.

Step

Check

Yes

No

EN(H4DOTC)(diag)-202

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

12

CHECK STATUS OF MALFUNCTION INDI-
CATOR LIGHT.
1) Clear the memory using the Subaru Select
Monitor or general scan tool. <Ref. to
EN(H4DOTC)(diag)-63, Clear Memory Mode.>
2) Start the engine, and drive the vehicle 10
minutes or more.

Does the malfunction indicator
light illuminate or blink?

Go to step

14.

Go to step

13.

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 MISFIRE SYMPTOM.
1) Turn the ignition switch to ON.
2) Check for DTC. <Ref. to
EN(H4DOTC)(diag)-48, Read Diagnostic Trou-
ble Code (DTC).>

Does the Subaru Select Moni-
tor or general scan tool indicate
only one DTC?

Go to step

18.

Go to step

16.

16

CHECK DTC.

Is DTC P0301 and P0303 dis-
played on the Subaru Select
Monitor or general scan tool?

Go to step

19.

Go to step

17.

17

CHECK DTC.

Is DTC P0302 and P0304 dis-
played on the Subaru Select
Monitor or general scan tool?

Go to step

20.

Go to step

21.

18

ONLY ONE CYLINDER.

Is there any fault in the cylin-
der?

Repair or replace
faulty parts.
NOTE:

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

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)-203

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

19

GROUP OF #1 AND #3 CYLINDERS.

Are there any faults in #1 and
#3 cylinders?

Repair or replace
faulty parts.
NOTE:

Check the follow-
ing items.
• Spark plug
• Ignition coil
• Fuel injector
• 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).>

20

GROUP OF #2 AND #4 CYLINDERS.

Are there any faults in #2 and
#4 cylinders?

Repair or replace
faulty parts.
NOTE:

Check the follow-
ing items.
• Spark plug
• Ignition coil
• Fuel injector
• 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).>

21

CYLINDER AT RANDOM.

Is the engine idle rough?

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).>

Repair or replace
faulty parts.
NOTE:

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

Step

Check

Yes

No