Subaru Legacy III (2000-2003 year). Manual - part 225

EN(H4SOw/oOBD)-90

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK HARNESS BETWEEN ECM AND 
TCM CONNECTOR.
1) Disconnect connectors from ECM and 

TCM.

2) Measure resistance of harness between 

ECM and chassis ground.

Connector & terminal

(B135) No. 17 — Chassis ground:

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

10 

Ω

Repair ground 
short circuit in har-
ness between 
ECM and TCM 
connector.

Go to step 2.

2

CHECK HARNESS BETWEEN ECM AND 
TCM CONNECTOR.
Measure resistance of harness between ECM 
and chassis ground.

Connector & terminal

(B135) No. 16 — Chassis ground:

Is the measured value less than the specified 
value?

10 

Ω

Repair ground 
short circuit in har-
ness between 
ECM and TCM 
connector.

Replace TCM.  
<Ref. to AT-76, 
Transmission Con-
trol Module 
(TCM).>

EN(H4SOw/oOBD)-91

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

M: DTC 45 PRESSURE SENSOR

• DIAGNOSIS:

• The pressure sensor signal is abnormal.
• The harness connector between ECM and pressure 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-01055

16

15

13

5

INTAKE AIR

TEMPERATURE

AND

PRESSURE

SENSOR

4
6

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

B136

B83

9

15

14

12

B21

E2

1

4

2

3

E21

B83

E20

1 2 3 4

ECM

B21

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

B136

EN(H4SOw/oOBD)-92

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK HARNESS BETWEEN ECM AND 
PRESSURE SENSOR CONNECTOR.
1) Disconnect connector from pressure sen-

sor.

2) Turn ignition switch to ON.
3) Measure voltage between pressure sensor 

connector and engine ground.

Connector & terminal

(E20) No. 3 (+) — Engine ground (–):

Is the measured value within the specified 
value?

4.5 — 5.5 V

Go to step 2.

Repair open or 
ground short cir-
cuit in harness 
between ECM and 
pressure sensor.

2

CHECK HARNESS BETWEEN ECM AND 
PRESSURE SENSOR CONNECTOR.
1) Disconnect connector from ECM.
2) Measure resistance of harness between 

ECM and pressure sensor connector.

Connector & terminal

(B136) No. 16 — (E20) No. 1:
(B136) No. 5 — (E20) No. 4:

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

1 

Ω

Go to step 3.

Repair open circuit 
in harness 
between ECM and 
pressure sensor 
connector.

3

CHECK HARNESS BETWEEN ECM AND 
PRESSURE SENSOR CONNECTOR.
Measure resistance of harness between ECM 
connector and chassis ground.

Connector & terminal

(B136) No. 5 — Chassis ground:
(B136) No. 16 — Chassis ground:

Does the measured value exceed the specified 
value?

1 M

Ω

Go to step 4.

Repair ground 
short circuit in har-
ness between 
ECM and pressure 
sensor connector.

4

CHECK INPUT SIGNAL FOR ECM.
1) Turn ignition switch to OFF.
2) Connect connector to ECM and pressure 

sensor.

3) Turn ignition switch to ON.
4) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B136) No. 5 (+) — Chassis ground (–):

Is the measured value within the specified 
value?

2.3 — 2.5 V

Go to step 5.

Replace pressure 
sensor.  <Ref. to 
FU(H4SOw/
oOBD)-32, Intake 
Air Temperature 
and Pressure Sen-
sor.>

5

CHECK INPUT SIGNAL FOR ECM.
1) Start engine, and idle it.
2) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B136) No. 5 (+) — Chassis ground (–):

Is the measured value within the specified 
value?

1.2 — 1.8 V

Go to step 6.

Replace pressure 
sensor.  <Ref. to 
FU(H4SOw/
oOBD)-32, Intake 
Air Temperature 
and Pressure Sen-
sor.>

6

CHECK POOR CONTACT.
Check poor contact in pressure sensor con-
nector.
Is there poor contact in pressure sensor con-
nector?

There is poor contact.

Repair poor con-
tact in pressure 
sensor connector.

Replace pressure 
sensor.  <Ref. to 
FU(H4SOw/
oOBD)-32, Intake 
Air Temperature 
and Pressure Sen-
sor.>

EN(H4SOw/oOBD)-93

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

N: DTC 46 CO RESISTOR (GENERAL SPEC. VEHICLES)

• DIAGNOSIS:

• The CO resistor signal is abnormal.
• The harness connector between ECM and CO resistor is in short or open.
• The CO value is not adjusted to specifications.

• TROUBLE SYMPTOM:

• Erroneous idling
• Mixture ratio is too rich or too lean.

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-01061

16

12

15

B136

3

2

1

B155

CO RESISTOR

B83

6

5

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

B136

ECM

1 2 3 4 5 6 7 8 9 10 11 12

B155

1 2 3