Subaru Legacy IV (2008 year). Service manual — part 364

EN(H4DOTC)(diag)-277

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?

Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(H4DOTC)(diag)
-81, List of Diag-
nostic Trouble
Code (DTC).>

Go to step 2.

2

CHECK ENGINE OIL.

Is there a proper amount of
engine oil?

Go to step 3.

Replace engine oil.
<Ref. to
LU(H4SO)-10,
REPLACEMENT,
Engine Oil.>

3

CHECK EXHAUST SYSTEM.

Are there holes or loose bolts
on exhaust system?

Repair the exhaust
system.

Go to step 4.

4

CHECK AIR INTAKE SYSTEM.

Are there holes, loose bolts or
disconnection of hose on air
intake system?

Repair the air
intake system.

Go to step 5.

5

CHECK FUEL PRESSURE.

WARNING:
Place “NO OPEN FLAMES” signs near the
working area.

CAUTION:
Be careful not to spill fuel.
Measure the fuel pressure while disconnecting
pressure regulator vacuum hose from intake
manifold. <Ref. to ME(H4DOTC)-25, INSPEC-
TION, Fuel Pressure.>

CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.

NOTE:
If fuel pressure does not increase, squeeze the
fuel return hose 2 to 3 times, then measure fuel
pressure again.

Is the measured value 284 —
314 kPa (2.9 — 3.2 kg/cm

2

,

41 — 46 psi)?

Go to step 6.

Repair the follow-
ing item.
Fuel pressure is
too high:
• Clogged fuel
return line or bent
hose
Fuel pressure is
too low:
• Improper fuel
pump discharge
• Clogged fuel
supply line

6

CHECK FUEL PRESSURE.
After connecting the pressure regulator vacuum
hose, measure fuel pressure. <Ref. to
ME(H4DOTC)-25, 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 (2.35 — 2.65 kg/cm

2

,

33 — 38 psi)?

Go to step 7.

Repair the follow-
ing item.
Fuel pressure is
too high:
• Faulty pressure
regulator
• Clogged fuel
return line or bent
hose
Fuel pressure is
too low:
• Faulty pressure
regulator
• Improper fuel
pump discharge
• Clogged fuel
supply line

EN(H4DOTC)(diag)-278

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

7

CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm up completely.
2) Read the data of engine coolant tempera-
ture sensor signal using Subaru Select Monitor
or general scan tool.

NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-34, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.

Is the engine coolant tempera-
ture 75°C (167°F) or higher?

Go to step 8.

Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(H4DOTC)-31,
Engine Coolant
Temperature Sen-
sor.>

8

CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 70°C (158°F).
2) For AT models, set the select lever to “P”
range or “N” range, and for MT models, place
the shift lever in the neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the data of the mass air flow and
intake air temperature sensor signal using Sub-
aru Select Monitor or general scan tool.

NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-34, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.

Is the measured value 2.0 —
5.0 g/s (0.26 — 0.66 lb/m)?

Go to step 9.

Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(H4DOTC)-36,
Mass Air Flow and
Intake Air Temper-
ature Sensor.>

9

CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 70°C (158°F).
2) For AT models, set the select lever to “P”
range or “N” range, and for MT models, place
the shift lever in the 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 data of the mass air flow and
intake air temperature sensor signal using Sub-
aru Select Monitor or general scan tool.

NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-34, 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 temperature. Is
the obtained value –10 — 50°C
(–18 — 90°F)?

Go to step 10.

Check the mass air
flow and intake air
temperature sen-
sor. <Ref. to
FU(H4DOTC)-36,
Mass Air Flow and
Intake Air Temper-
ature Sensor.>

Step

Check

Yes

No

EN(H4DOTC)(diag)-279

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

10

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 15.

Go to step 11.

11

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 12.

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

12

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 13.

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

13

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 14.

Replace the faulty
fuel injector. <Ref.
to FU(H4DOTC)-
38, Fuel Injector.>

14

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
main relay and fuel
injector connector
on faulty cylinders
• Poor contact of
coupling connector
• Poor contact of
main relay connec-
tor

Step

Check

Yes

No

EN(H4DOTC)(diag)-280

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

15

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
the harness
between the ECM
and fuel injector.

Go to step 16.

16

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(H4DOTC)-
38, Fuel Injector.>

Go to step 17.

17

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.

Go to step 18.

18

CHECK CRANK SPROCKET.
Remove the timing belt cover. <Ref. to
ME(H4DOTC)-46, REMOVAL, Timing Belt
Cover.>

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

Replace the crank
sprocket. <Ref. to
ME(H4DOTC)-57,
Crank Sprocket.>

Go to step 19.

19

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(H4DOTC)-47,
Timing Belt.>

Go to step 20.

20

CHECK ELECTRONIC THROTTLE CON-
TROL RELAY.
1) Turn the ignition switch to OFF.
2) Remove the electronic throttle control relay.
3) Connect the battery to terminals No. 5 and
No. 6 of electronic throttle control relay.
4) Measure the resistance between electronic
throttle control relay terminals.

Terminals

No. 7 — No. 8:

Is the resistance less than 1

:? Go to step 21.

Replace the elec-
tronic throttle con-
trol relay. <Ref. to
FU(H4DOTC)-55,
Electronic Throttle
Control Relay.>

21

CHECK POWER SUPPLY OF ELECTRONIC
THROTTLE CONTROL RELAY.
Measure the voltage between electronic throttle
control relay connector and chassis ground.

Connector & terminal

(E362) No. 7 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step 22.

Repair the open or
ground short circuit
of power supply
circuit.

22

CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY.
1) Disconnect the connectors from ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between electronic
throttle control relay connector and chassis
ground.

Connector & terminal

(B362) No. 6 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Repair the short
circuit to power in
harness between
ECM and elec-
tronic throttle con-
trol relay.

Go to step 23.

Step

Check

Yes

No