Subaru Legacy (2005 year). Service manual — part 326

EN(H4DOTC)(diag)-73

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

5

CHECK REAR OXYGEN SENSOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between rear oxy-
gen sensor connector terminals.

Terminals

No. 1 — No. 2:

Is the resistance less than 30
Ω?

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• Open circuit of
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 the rear
oxygen sensor.
<Ref. to
FU(H4DOTC)-33,
Rear Oxygen Sen-
sor.>

Step

Check

Yes

No

EN(H4DOTC)(diag)-74

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

D: DTC P0038 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 2)

DTC DETECTING CONDITION:
Detects when malfunction occurs in 2 continuous driving cycles.

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
37, OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOTC)(diag)-30, PROCE-
DURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-03555

1 2 3 4
5 6 7 8

B83

BATTERY

MAIN RELAY

B47

1

2

4

6

3

5

E

E

B21

E2

35

*

*

B83

3

4

1

2

5

6

B135

B47

B19

B136

1

4

2

3

T6

REAR
OXYGEN SENSOR

B4

B1

B2

D25

D31

C35

ECM

B136

B137

C:

B135

B:

D:

1

2

3

4

B:

C:

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

35

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

29 30 31

32 33

34 35

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

B19

T5

2

T5

B19

3

1

4

B21

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

T6

2 1
4 3

*

: TERMINAL No. RANDOM ARRANGEMENT

EN(H4DOTC)(diag)-75

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

Step

Check

Yes

No

1

CHECK GROUND CIRCUIT FOR ECM.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness
between ECM connector and chassis ground.

Connector & terminal

(B135) No. 4 — Chassis ground:
(B135) No. 1 — Chassis ground:

Is the resistance less than 5
Ω?

Go to step 2.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• Open circuit of
harness between
ECM and engine
ground cable
• Poor contact in
ECM connector
• Poor contact in
coupling connector

2

CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR.
Measure the voltage between ECM and chas-
sis ground.

Connector & terminal

(B135) No. 2 (+) — Chassis ground (

−

):

Is the voltage more than 10 V? Repair the battery

short circuit of har-
ness between
ECM and rear oxy-
gen sensor.

Repair the poor
connection in ECM
connector.

EN(H4DOTC)(diag)-76

ENGINE (DIAGNOSTICS)

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

E: DTC P0102 MASS OR VOLUME AIR FLOW CIRCUIT LOW INPUT

DTC DETECTING CONDITION:
Immediately at fault recognition
TROUBLE SYMPTOM:
• Erroneous idling
• Engine stalls.
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
37, OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOTC)(diag)-30, PROCE-
DURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-03523

B3

E

B83

1

B3

ECM

B136

SBF-7

1 2 3 4 5

3

4

1

2

5

6

B136

B47

*

*

2

4

3

5

31

13

23

35

32

B47

1

2

4

6

3

5

1 2 3 4
5 6 7 8

B83

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

35

BATTERY

MASS AIR FLOW AND

INTAKE AIR TEMPERATURE

SENSOR

MAIN RELAY

*

: TERMINAL No. RANDOM ARRANGEMENT