Subaru Legacy IV (2008 year). Manual - part 587

EN(H6DO)(diag)-321

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

9

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 10.

10

CHECK FUEL PRESSURE.

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

CAUTION:
Be careful not to spill fuel.
1) Connect the front oxygen (A/F) sensor con-
nector.
2) Measure the fuel pressure. <Ref. to 
ME(H6DO)-27, INSPECTION, Fuel Pressure.>

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

Is the measured value 333 — 
343 kPa (3.4 — 3.5 kgf/cm

2

,

48.4 — 49.8 psi)?

Go to step 11.

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

11

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(H6DO)(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 12.

Replace the 
engine coolant 
temperature sen-
sor. <Ref. to 
FU(H6DO)-20, 
Engine Coolant 
Temperature Sen-
sor.>

12

CHECK MASS AIR FLOW AND INTAKE AIR 
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until 
coolant temperature is higher than 75°C 
(167°F).
2) Place the select lever in “P” range or “N” 
range.
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(H6DO)(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 13.

Replace the mass 
air flow and intake 
air temperature 
sensor. <Ref. to 
FU(H6DO)-26, 
Mass Air Flow and 
Intake Air Temper-
ature Sensor.>

Step

Check

Yes

No

EN(H6DO)(diag)-322

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

13

CHECK MASS AIR FLOW AND INTAKE AIR 
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until 
coolant temperature is higher than 75°C 
(167°F).
2) Place the select lever in “P” range or “N” 
range.
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(H6DO)(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 14.

Check the mass air 
flow and intake air 
temperature sen-
sor. <Ref. to 
FU(H6DO)-26, 
Mass Air Flow and 
Intake Air Temper-
ature Sensor.>

14

CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant 
temperature is above 75°C (167°F), and keep 
the engine speed at 3,000 rpm. (for up to 2 min-
utes)
2) Read the data of rear oxygen 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(H6DO)(diag)-34, Subaru Select Moni-
tor.>
• General Scan Tool
For detailed operation procedures, refer to the
general scan tool operation manual.

Is the voltage 490 mV or more? Go to step 15.

Go to step 16.

15

CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant 
temperature is above 75°C (167°F), and rapidly 
reduce the engine speed from 3,000 rpm.
2) Read the data of rear oxygen 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(H6DO)(diag)-34, Subaru Select Moni-
tor.>
• General Scan Tool
For detailed operation procedures, refer to the
general scan tool operation manual.

Is the voltage 250 mV or less?

Go to step 17.

Go to step 16.

16

CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.

Has water entered the connec-
tor?

Completely 
remove any water 
inside.

Go to step 18.

Step

Check

Yes

No

EN(H6DO)(diag)-323

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

17

CHECK FRONT OXYGEN (A/F) SENSOR 
AND REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant 
temperature is higher than 75°C (167°F), then 
keep the engine idling for 5 minutes or more.
2) Read the data of rear oxygen 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(H6DO)(diag)-34, Subaru Select Moni-
tor.>
• General Scan Tool
For detailed operation procedures, refer to the
general scan tool operation manual.

Is a voltage of 0.8 V or more 
maintained for 5 minutes or 
more?

Replace the front 
oxygen (A/F) sen-
sor. <Ref. to 
FU(H6DO)-32,
Front Oxygen (A/F) 
Sensor.>

Go to step 18.

18

CHECK HARNESS BETWEEN ECM AND 
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and 
rear oxygen sensor.
3) Measure the resistance of harness between 
ECM and rear oxygen sensor connector.

Connector & terminal

(B135) No. 15 — (E25) No. 3:
(B135) No. 30 — (E25) No. 4:

Is the resistance less than 1 

:? Go to step 19.

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and rear oxy-
gen sensor con-
nector
• Poor contact of
coupling connector

19

CHECK HARNESS BETWEEN ECM AND 
REAR OXYGEN SENSOR CONNECTOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen 
sensor connector and chassis ground.

Connector & terminal

(E25) No. 3 (+) — Chassis ground (–):

Is the voltage 0.2 — 0.5 V?

Replace the rear 
oxygen sensor. 
<Ref. to 
FU(H6DO)-34,
Rear Oxygen Sen-
sor.>

Repair the harness 
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
the ECM and rear
oxygen sensor
• Poor contact in
ECM connector
• Poor contact of
coupling connector

Step

Check

Yes

No

EN(H6DO)(diag)-324

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

EB:DTC P2101 THROTTLE ACTUATOR CONTROL MOTOR CIRCUIT RANGE/

PERFORMANCE

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H6DO)-191, DTC P2101 THROTTLE ACTUATOR CONTROL
MOTOR CIRCUIT RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Improper idling
• Poor driving performance
• Engine stalls.

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H6DO)(diag)-52,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H6DO)(diag)-44, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

B20

1 2 3 4 5 6

E57

1 2 3 4
5 6 7 8

B122

1 2

7 8

3
4

5
6

B362

36

52

34

35

37

E

E2

B21

E

A5

C21

C1

A29

19

E1

B20

A18

C6

A28

6

4

15

*

*

B122

16

E

38

39

20

D5

D4

A19

D7

D1

A3

D2

D3

3

E57

ELECTRONIC THROTTLE 

CONTROL

2

1

5

B134

B362

5

7

6

A:

B137

B136

D:

C:

ECM

*

: TERMINAL No. OPTIONAL ARRANGEMENT

E

SBF-7

BATTERY

ELECTRONIC 
THROTTLE
CONTROL RELAY

MAIN RELAY

8

6

4

B47

B47

3

4

1

2

5

6

EN-06873

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

B136

C:

5

6

7

8

2

1

9

4

3

10

22 23

11 12 13 14 15

24 25

26

16 17

18 19 20 21

27

28 29

30 31

B137

D:

5

6

7

8

2

1

9

4

3

10

24

22 23

25

11 12 13 14 15

26 27

28

16 17

18 19 20 21

33 34

29

32

30 31

B134

A:

B21

1 2 3 4 5 6 7 8 9 10 11

12 13 14 15 16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33

34

35

42

43

36

37

38

39

48

49

50

51

52

53

54

40

41

44

45

46

47