Subaru Legacy III (2000-2003 year). Manual - part 222

EN(H4SOw/oOBD)-78

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

6

CHECK HARNESS BETWEEN ECM AND IN-
TAKE AIR TEMPERATURE SENSOR CON-
NECTOR.
Measure resistance of harness between ECM 
connector and chassis ground.

Connector & terminal

(B136) No. 13 — Chassis ground:

Does the measured value exceed the specified 
value?

1 M

Ω

Go to step 7.

Repair ground 
short circuit in har-
ness between 
ECM and idle air 
control solenoid 
valve connector.

7

CHECK POOR CONTACT.
Check poor contact in ECM connector.
Is there poor contact in ECM connector?

There is poor contact.

Repair poor con-
tact in ECM con-
nector.

Contact with your 
Subaru distributor.

NOTE:
Inspection by your
Subaru distributor
is required, be-
cause probable
cause is deteriora-
tion of multiple
parts.

Step

Value

Yes

No

EN(H4SOw/oOBD)-79

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

H: DTC 31 THROTTLE POSITION SENSOR

• DIAGNOSIS:

• The throttle position sensor signal is abnormal.
• The throttle position sensor is installed abnormally.
• The harness connector between ECM and throttle position sensor is in short or open.

• TROUBLE SYMPTOM:

• Erroneous idling
• Engine stalls
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, conduct CLEAR MEMORY and INSPECTION MODES. <Ref. 
to EN(H4SOw/oOBD)-28, OPERATION, Clear Memory Mode.>  and <Ref. to EN(H4SOw/oOBD)-26, OP-
ERATION, Inspection Mode.>
• WIRING DIAGRAM:

EN-01056

16

17

15

9

11

12

B136

2

3

4

B21

E2

E13

THROTTLE

POSITION

SENSOR

E13

B83

1 2 3 4

6

4

B83

5

4

6 7

8

2

1

9

3

10

22

23

11 12 13 14 15

24 25

26 27

16 17 18

28 29

19 20

21

30

B21

B136

ECM

1 2

5

6 7

8

13

14 15

16

9 10

11 12

3 4

17 18

19 20

1 2 3 4 5 6 7 8 9 10 11 12

EN(H4SOw/oOBD)-80

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK CONDITION OF THROTTLE POSI-
TION SENSOR INSTALLATION.
Are the throttle position sensor installing screw 
tightened securely?

Installing screw is securely 
tightened.

Go to step 2.

Adjust throttle 
position sensor 
and tighten throt-
tle position sensor 
installing screws 
securely.

2

CHECK HARNESS BETWEEN ECM AND 
THROTTLE POSITION SENSOR.
1) Disconnect connector from ECM and throt-

tle position sensor.

2) Measure resistance between ECM and 

throttle position sensor.

Connector & terminal

(B136) No. 16 — (E13) No. 2:
(B136) No. 17 — (E13) No. 3:
(B136) No. 15 — (E13) No. 4:

Is the measured value less than the speci-
fied value?

1 

Ω

Go to step 3.

Repair open circuit 
between ECM and 
throttle position 
sensor.

3

CHECK HARNESS BETWEEN ECM AND 
THROTTLE POSITION SENSOR CONNEC-
TOR.
1) Disconnect connector from TCM. (AT vehi-

cle)

2) Measure resistance between ECM and 

chassis ground.

Connector & terminal

(B136) No. 16 — Chassis ground:
(B136) No. 17 — Chassis ground:
(B136) No. 15 — Chassis ground:

Does the measured value exceed the spec-
ified value?

1 M

Ω

Go to step 4.

Repair ground 
short circuit 
between ECM and 
chassis ground.

4

CHECK INPUT SIGNAL FOR ECM.
1) Connect connector to ECM and throttle 

position sensor.

2) Ignition switch to ON.
3) Measure voltage between ECM terminals 

while throttle valve is fully closed.

Connector & terminal

(B136) No. 17 — No. 15:

Is the measured value less than the speci-
fied value?

 0.1 V

Go to step 6.

Go to step 5.

5

CHECK INPUT SIGNAL FROM ECM.
Measure voltage between ECM terminals 
while throttle valve is fully opened.

Connector & terminal

(B136) No. 17 — No. 15:

Does the measured value exceed the specified 
value?

4.5 V

Go to step 6.

Replace ECM.

6

CHECK POOR CONTACT.
Check poor contact in throttle position sensor 
connector.
Is there poor contact in throttle position sensor 
connector?

There is poor contact.

Repair poor con-
tact in throttle posi-
tion sensor 
connector.

Replace throttle 
position sensor.

EN(H4SOw/oOBD)-81

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

I:

DTC 32 OXYGEN SENSOR

• DIAGNOSIS:

• The oxygen sensor is not in function.
• The harness connector between ECM and oxygen sensor is in short or open.

• TROUBLE SYMPTOM:

• Failure of engine to start
• Erroneous idling
• Poor driving performance
• Engine stalls.
• Idle mixture is out of specifications.

CAUTION:
After repair or replacement of faulty parts, conduct CLEAR MEMORY and INSPECTION MODES. <Ref. 
to EN(H4SOw/oOBD)-28, OPERATION, Clear Memory Mode.>  and <Ref. to EN(H4SOw/oOBD)-26, OP-
ERATION, Inspection Mode.>
• WIRING DIAGRAM:

EN-01057

F44

B61

E3

B22

B47

B47

3

4

1

2

5

6

B136

B22

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

B18

F44

SBF-5

BATTERY

MAIN RELAY

1

2

3

5

4

6

6

LHD

LHD

RHD

RHD

1 2 3 4
5 6 7 8

23

7

ECM

OXYGEN SENSOR

2

4

1

B18

B136

15

1

2

3

4

5

4

6 7

8

2

1

9

3

10

22

23

11 12 13 14 15

24 25

26 27

16 17 18

28 29

19 20

21

30