Subaru Legacy III (2000-2003 year). Manual - part 327

EN(H6DO)-110

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

6

CHECK POWER SUPPLY TO REAR OXY-
GEN SENSOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from rear oxygen 

sensor.

3) Turn ignition switch to ON.
4) Measure voltage between rear oxygen sen-

sor connector and engine ground or chas-
sis ground.

Connector & terminal

(T6) No. 2 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 7.

Repair power sup-
ply line.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
main relay and 
rear oxygen sen-
sor connector
• Poor contact in 
rear oxygen sen-
sor connector
• Poor contact in 
coupling connector

7

CHECK REAR OXYGEN SENSOR.
1) Turn ignition switch to OFF.
2) Measure resistance between rear oxygen 

sensor connector terminals.

Terminals

No. 1 — No. 2:

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

30 

Ω

Repair harness 
and connector.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
rear oxygen sen-
sor and ECM con-
nector
• Poor contact in 
rear oxygen sen-
sor connector
• Poor contact in 
ECM connector
• Poor contact in 
coupling connector

Replace rear oxy-
gen sensor. <Ref. 
to FU(H6DO)-45, 
Rear Oxygen Sen-
sor.>

Step

Value

Yes

No

EN(H6DO)-111

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO:

EN(H6DO)-112

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

E: DTC P0038 — HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 

2) —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H6DO)-54, OP-
ERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H6DO)-47, OPERATION, Inspec-
tion Mode.>.
• WIRING DIAGRAM:

EN-01088

BATTERY

F44

B61

6

T5

B19

B47

MAIN RELAY

2
1

3

5

4

6

F44

1 2 3 4
5 6 7 8

C13

B17

B19
B26

D21

D31

D9

D8

REAR 

OXYGEN 

SENSOR

5

3

6
4

1

3

4

2

1

5

B252

B83

B19

T5

T6

E49

B47

T6

B136

C:

D:

B135

B:

3

4

5

6

1

2

5

7

ECM

B135

B:

B136

C:

B137

D:

3

4

1

2

1 2

7

8 9

5

6

3

4

10 11 12
19 20 21

13 14 15 16

17 18

22 23 24

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

B137

1

2

7

8

9

5

6

3

4

10 11 12

19 20 21
29 30 31

13 14 15 16 17

27 28

18

22 23 24 25 26

RHD

LHD

LHD

RHD

B252

1 2 3 4
5 6 7 8

B19

4

1 2 3

6

5

2

B83

1 2 3 4

5 6 7 8 9 10

11 12

19

20

13 14 15 16 17 18

EN(H6DO)-113

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK OUTPUT SIGNAL FROM ECM.
Measure voltage between ECM connector and 
chassis ground.

Connector & terminal

(B136) No. 13 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the specified 
value?

8 V

Go to step 2.

Go to step 3.

2

CHECK CURRENT DATA.
1) Repair battery short circuit in harness 

between ECM and rear oxygen sensor con-
nector.

2) Turn ignition switch to ON.
3) Read data of rear oxygen sensor heater 

current using Subaru Select Monitor or the 
OBD-II general scan tool.
Does the measured value exceed the spec-
ified value?

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to the 
“READ CURRENT DATA FOR ENGINE”. 
<Ref. to EN(H6DO)-34, Subaru Select Moni-
tor.>  
• OBD-II general scan tool
For detailed operation procedure, refer to the 
OBD-II General Scan Tool Instruction Manual.

7 A

Replace ECM. 
<Ref. to 
FU(H6DO)-46, 
Engine Control 
Module.>

END

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 con-
nector.

END