Subaru Legacy IV (2008 year). Manual — part 143

EN(H4SO)(diag)-175

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

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 (B137) No. 8 (+) — Chassis ground (–):
#2 (B137) No. 9 (+) — Chassis ground (–):
#3 (B137) No. 10 (+) — Chassis ground (–):
#4 (B137) No. 11 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step 6.

Go to step 2.

2

CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR.
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. 1 — Engine ground:
#2 (E16) No. 1 — Engine ground:
#3 (E6) No. 1 — Engine ground:
#4 (E17) No. 1 — Engine ground:

Is the resistance 1 M

: or

more?

Go to step 3.

Repair the ground
short circuit of har-
ness between
ECM and fuel
injector.

3

CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR.
Measure the resistance of harness between
ECM and fuel injector on faulty cylinders.

Connector & terminal

#1 (B137) No. 8 — (E5) No. 1:
#2 (B137) No. 9 — (E16) No. 1:
#3 (B137) No. 10 — (E6) No. 1:
#4 (B137) No. 11 — (E17) No. 1:

Is the resistance less than 1

:? Go to step 4.

Repair the harness
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
ECM and fuel in-
jector 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 between 5 —
20

:?

Go to step 5.

Replace the faulty
fuel injector. <Ref.
to FU(H4SO)-30,
Fuel Injector.>

5

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

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 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

EN(H4SO)(diag)-176

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

6

CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR.
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 (B137) No. 8 (+) — Chassis ground (–):
#2 (B137) No. 9 (+) — Chassis ground (–):
#3 (B137) No. 10 (+) — Chassis ground (–):
#4 (B137) No. 11 (+) — Chassis ground (–):

Is the voltage 10 V or more?

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

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 less than 1

:? Replace the faulty

fuel injector. <Ref.
to FU(H4SO)-30,
Fuel Injector.>

Go to step 8.

8

CHECK INSTALLATION CONDITION OF
CAMSHAFT POSITION SENSOR/CRANK-
SHAFT POSITION SENSOR.

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

Tighten the cam-
shaft position sen-
sor or crankshaft
position sensor.

Go to step 9.

9

CHECK CRANK SPROCKET.
Remove the timing belt cover. <Ref. to
ME(H4SO)-43, REMOVAL, Timing Belt Cover.>

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

Replace the crank
sprocket. <Ref. to
ME(H4SO)-50,
Crank Sprocket.>

Go to step 10.

10

CHECK INSTALLATION CONDITION OF
TIMING BELT.
Turn the crankshaft using ST, and align the
alignment mark on crank sprocket with align-
ment mark on cylinder 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(H4SO)-44,
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 fuel meter indi-
cation is higher
than the “Lower”
level. After replen-
ishing fuel, Go to
step 12.

12

CHECK STATUS OF MALFUNCTION INDI-
CATOR LIGHT.
1) Clear the memory using the Subaru Select
Monitor or general scan tool.
<Ref. to EN(H4SO)(diag)-50, Clear Memory
Mode.>

NOTE:
• SUBARU SELECT MONITOR
<Ref. to EN(H4SO)(diag)-33, Subaru Select
Monitor.>
• General Scan Tool
Refer to the general scan tool operation manu-
al.
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.

Step

Check

Yes

No

EN(H4SO)(diag)-177

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 in
fuel injector con-
nector on faulty
cylinders
• Poor contact in
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) Read the DTC.

NOTE:
• SUBARU SELECT MONITOR
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4SO)(diag)-33, Subaru Select Moni-
tor.>
• General Scan Tool
For detailed operation procedures, refer to the
general scan tool operation manual.

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

Go to step 20.

Go to step 16.

16

CHECK DTC.

Are DTC P0301 and P0302 dis-
played on the Subaru Select
Monitor or general scan tool?

Go to step 21.

Go to step 17.

17

CHECK DTC.

Are DTC P0303 and P0304 dis-
played on the Subaru Select
Monitor or general scan tool?

Go to step 22.

Go to step 18.

18

CHECK DTC.

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

Go to step 23.

Go to step 19.

19

CHECK DTC.

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

Go to step 24.

Go to step 25.

Step

Check

Yes

No

EN(H4SO)(diag)-178

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

20

ONLY ONE CYLINDER.

Is there any fault in the cylin-
der?

Repair or replace
faulty parts.

NOTE:
Check the follow-
ing items.
• Spark plug
• Spark plug cord
• Fuel injector
• Compression ra-
tio

Go to DTC P0171.
<Ref. to
EN(H4SO)(diag)-
155, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>

21

GROUP OF #1 AND #2 CYLINDERS.

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

Repair or replace
faulty parts.

NOTE:
• Check the fol-
lowing items.

• Spark plug
• Fuel injector
• Ignition coil
• Compression
ratio

• If any fault are
not found, check
the “IGNITION
CONTROL SYS-
TEM” of #1 and #2
cylinders side.
<Ref. to
EN(H4SO)(diag)-
71, IGNITION
CONTROL SYS-
TEM, Diagnostics
for Engine Starting
Failure.>

Go to DTC P0171.
<Ref. to
EN(H4SO)(diag)-
155, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>

22

GROUP OF #3 AND #4 CYLINDERS.

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

Repair or replace
faulty parts.

NOTE:
• Check the fol-
lowing items.

• Spark plug
• Fuel injector
• Ignition coil
• Compression
ratio

• If any fault are
not found, check
the “IGNITION
CONTROL SYS-
TEM” of #3 and #4
cylinders side.
<Ref. to
EN(H4SO)(diag)-
71, IGNITION
CONTROL SYS-
TEM, Diagnostics
for Engine Starting
Failure.>

Go to DTC P0171.
<Ref. to
EN(H4SO)(diag)-
155, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>

Step

Check

Yes

No