Subaru Legacy III (2000-2003 year). Manual - part 223

EN(H4SOw/oOBD)-82

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK FOR OTHER CAUSES AFFECTING 
EXHAUST GAS.
1) Check for use of improper fuel.
2) Check if engine oil or coolant level is 

extremely low.
Does CO% after warm-up exceed the spec-
ified value?

2%

Check fuel sys-
tem.

Go to step 2.

2

CHECK EXHAUST SYSTEM.
Is there a fault in exhaust system?

The system is faulty.

Repair exhaust 
system.

NOTE:
• Loose installa-
tion of front portion 
of exhaust pipe 
onto cylinder 
heads
• Loose connec-
tion between front 
exhaust pipe and 
front catalytic con-
verter
• Damage of 
exhaust pipe 
resulting in hole

Go to step 3.

3

CHECK INPUT VOLTAGE FOR OXYGEN 
SENSOR.
1) Disconnect connector from oxygen sensor 

connector.

2) Measure voltage between main relay and 

oxygen sensor.

Connector & terminal

(B18) No. 2 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 4.

Repair open circuit 
between main 
relay and oxygen 
sensor.

4

CHECK HARNESS CONNECTOR BETWEEN 
OXYGEN SENSOR AND ENGINE GROUND 
TERMINAL.
Measure resistance between oxygen sensor 
and chassis ground.

Connector & terminal

(B18) No. 1 — Chassis ground:

Is the measured value less than the specified 
value?

1

Ω

Go to step 5.

Repair open circuit 
between oxygen 
sensor and chas-
sis ground.

5

CHECK OXYGEN SENSOR.
Measure resistance between oxygen sensor 
terminals.

Connector & terminal

No. 1 — No. 2:

Is the measured value less than the specified 
value?

30 

Ω

Repair poor con-
tact.

Go to step 6.

6

CHECK HARNESS BETWEEN ECM AND OX-
YGEN SENSOR.
1) Disconnect connector from ECM.
2) Measure resistance between ECM and 

chassis ground.

Connector & terminal

(B136) No. 7 — Chassis ground:

Does the measured value exceed the spec-
ified value?

1 M

Ω

Go to step 7.

Repair ground 
short circuit 
between ECM and 
chassis ground.

EN(H4SOw/oOBD)-83

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

7

CHECK HARNESS BETWEEN ECM AND OX-
YGEN SENSOR.
1) Ignition switch to ON.
2) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B136) No. 7 (+) — Chassis ground (–):

Does the measured value exceed the spec-
ified value?

0.2 V

Go to step 8.

Repair battery 
short circuit 
between ECM and 
oxygen sensor.

8

CHECK INPUT VOLTAGE FOR ECM.
1) Turn ignition switch OFF.
2) Warm up engine until coolant temperature 

exceed 70

°

C (158

°

F) and idle.

3) Set plus (+) probe to ECM connector termi-

nal, and set minus (

−

) probe to chassis 

ground.

Connector & terminal

(B136) No. 7 (+) — Chassis ground (

−−−−

):

4) Measure voltage between ECM and chas-

sis ground.
Is the measured waveform standard?

0.1 

←

→

 1 V

Go to step 9.

Replace oxygen 
sensor.

9

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

There is poor contact.

Replace oxygen 
sensor connector.

Replace ECM.  
<Ref. to 
FU(H4SOw/
oOBD)-42, Engine 
Control Module.>

Step

Value

Yes

No

EN(H4SOw/oOBD)-84

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

J: DTC 33 VEHICLE SPEED SIGNAL

• DIAGNOSIS:

• The vehicle speed signal is abnormal.
• The harness connector between ECM and vehicle speed 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-01058

B36

i1

i10

B157

B17

B56

B36

i10

B22

B135

BATTERY

E4

13

24

ECM

COMBINATION
METER

VEHICLE 
SPEED
SENSOR

3

1

2

B17

B135

17

TCM

B56

IGNITION 
RELAY

No. 5

B157

B22

E3

16

MT

AT

1 2 3

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

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

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

1 2

7

8

9

5 6

3 4

10 11 12
19 20 21

13

14 15

16

17

18

22

23

24

B4 B5 B6

A4 A5 A6

C5 C6

F6

D4 D5 D6

F1

H1

C4

G6

G1

C2

K1

M1 M2

K6

L1

D1 D2

A1 A2
B1 B2

I6

J6

L2

I1

J1

H6

M4 M5 M6

L4 L5 L6 

N5 N6

O4 O5 O6

N4

P4 P5

N2

O1 O2

P1 P2

N3

O3

P3

P6

A3

B3

C3

E4 E5 E6

E1 E2

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 36

37
38

1

2

9

3

4

5

6

7

8

1

*

2

*

1

*

2

*

LHD : 9
RHD : 38

LHD : 10
RHD : 37

EN(H4SOw/oOBD)-85

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK SPEEDOMETER OPERATION IN 
COMBINATION METER.
Does speedometer operate normally?

Speedometer operates nor-
mally.

Go to step 2.

Check speedome-
ter and vehicle 
speed sensor.

2

CHECK INPUT SIGNAL FOR ECM.
1) Lift-up the vehicle.
2) Set the positive (+) terminal and earth lead 

of oscilloscope at ECM connector terminals 
and chassis ground.

Connector & terminal

(B135) No. 24 (+) — Chassis ground (–):

3) Start the engine.
4) Shift on the gear position, and put the vehi-

cle at constant speed.

5) Measure signal voltage indicated on oscillo-

scope.
Does the measured value exceed the spec-
ified value?

3 V

Go to step 3.

Go to step 4.

3

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.

Replace ECM.  
<Ref. to 
FU(H4SOw/
oOBD)-42, Engine 
Control Module.>

4

CHECK HARNESS BETWEEN ECM AND 
COMBINATION METER CONNECTOR.
Measure voltage between ECM and chassis 
ground.

Connector & terminal

(B135) No. 24 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the specified 
value?

2 V

Repair harness 
and connector.

NOTE:
In this case, repair
the following:
Battery short cir-
cuit in harness 
between ECM and 
combination meter 
connector

Go to step 5.

5

CHECK HARNESS BETWEEN ECM AND 
COMBINATION METER CONNECTOR.
1) Turn ignition switch to OFF.
2) Measure resistance of harness between 

ECM connector and chassis ground.

Connector & terminal

(B135) No. 24 — Chassis ground:

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

10 

Ω

Repair ground 
short circuit in har-
ness between 
ECM and combi-
nation meter con-
nector.

Go to step 6.

6

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.

Replace ECM.  
<Ref. to 
FU(H4SOw/
oOBD)-42, Engine 
Control Module.>