Subaru Legacy IV (2008 year). Service manual — part 586

EN(H6DO)(diag)-317

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

DZ:DTC P2098 POST CATALYST FUEL TRIM SYSTEM TOO LEAN BANK 2

NOTE:
Refer to DTC P2099 for diagnostic procedure. <Ref. to EN(H6DO)(diag)-318, DTC P2099 POST CATALYST
FUEL TRIM SYSTEM TOO RICH BANK 2, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>

17

CHECK FRONT OXYGEN (A/F) SENSOR
AND REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), then
keep the engine idling for 5 minutes or more.
2) Read the data of rear oxygen sensor signal
using Subaru Select Monitor or general scan
tool.

NOTE:
• SUBARU SELECT MONITOR
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H6DO)(diag)-34, Subaru Select Moni-
tor.>
• General Scan Tool
For detailed operation procedures, refer to the
general scan tool operation manual.

Is a voltage of 0.8 V or more
maintained for 5 minutes or
more?

Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(H6DO)-32,
Front Oxygen (A/F)
Sensor.>

Go to step 18.

18

CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM and rear oxygen sensor connector.

Connector & terminal

(B135) No. 4 — (E61) No. 3:
(B135) No. 30 — (E61) No. 4:

Is the resistance less than 1

:? Go to step 19.

Repair the harness
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and rear oxy-
gen sensor con-
nector
• Poor contact of
coupling connector

19

CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.

Connector & terminal

(E61) No. 3 (+) — Chassis ground (–):

Is the voltage 0.2 — 0.5 V?

Replace the rear
oxygen sensor.
<Ref. to
FU(H6DO)-34,
Rear Oxygen Sen-
sor.>

Repair the harness
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit of
harness between
the ECM and rear
oxygen sensor
• Poor contact in
ECM connector
• Poor contact of
coupling connector

Step

Check

Yes

No

EN(H6DO)(diag)-318

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

EA:DTC P2099 POST CATALYST FUEL TRIM SYSTEM TOO RICH BANK 2

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H6DO)-190, DTC P2099 POST CATALYST FUEL TRIM SYS-
TEM TOO RICH BANK 2, Diagnostic Trouble Code (DTC) Detecting Criteria.>

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H6DO)(diag)-52,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H6DO)(diag)-44, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

SBF-5

BATTERY

E

E3

B22

B47

1

2

3

5

4

6

MAIN RELAY

E3

B22

8

: TERMINAL No. OPTIONAL ARRANGEMENT
AMONG 1, 2, 5 AND 6

*

3

4

5

6

1

2

B47

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

B22

3 4

1 2

E47

E24

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

B136

C:

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

B137

D:

1 2 3 4
5 6 7 8

B138

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

B135

B:

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

B134

A:

B11

2

E24

FRONT

OXYGEN (A/F)

SENSOR LH

3

4

B10

1

B7

B6

C2

C3

B8

4

1

3

B9

ECM

B135

B:

B134

A:

B137

D:

B136

C:

D3

A3

D2

D1

D7

A5

35

34

52

36

37

B21

E2

E

E

EN-06867

B21

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 31 32 33

34

35

42

43

36

37

38

39

48

49

50

51

52

53

54

40

41

44

45

46

47

2

E47

FRONT

OXYGEN (A/F)

SENSOR RH

5

6

7

4

2

1

3

B138

*

*

B1

EN(H6DO)(diag)-319

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

B47

3

4

5

6

1

2

B22

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

1 2 3 4
5 6 7 8

B83

B138

3 4

1 2

E25

E61

B47

1

2

3

5

4

6

E3

B22

14

MAIN RELAY

2

4

3

1

E25

13

15

16

E3

B22

10

11

12

9

SBF-5

BATTERY

2

E61

4

3

1

*

1

*

1

*

1

B83

B138

ECM

B134

A:

B135

B:

B136

C:

B137

D3

A3

D2

D1

D7

A5

D:

C5

*

*

2

2

C4

E

B1

B15

B4

B30

35

34

52

36

37

B21

E2

E

E

: TERMINAL No. OPTIONAL ARRANGEMENT

*

1

: TERMINAL No. OPTIONAL ARRANGEMENT
AMONG 1, 2, 5 AND 6

*

2

EN-06868

16

10 11 12 13 14 15

25

24

30

9

8

7

17 18 19 20
28

21 22 23

29

32

31

1

2

3

4

5

6

27

26

33 34 35

B136

C:

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

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

29 30 31

32 33

34 35

B135

B:

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

B134

A:

B21

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 31 32 33

34

35

42

43

36

37

38

39

48

49

50

51

52

53

54

40

41

44

45

46

47

REAR
OXYGEN
SENSOR LH

REAR
OXYGEN
SENSOR RH

EN(H6DO)(diag)-320

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed?

Check DTC using
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(H6DO)(diag)-
81, List of Diagnos-
tic Trouble Code
(DTC).>

Go to step 2.

2

CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.

Has water entered the connec-
tor?

Completely
remove any water
inside.

Go to step 3.

3

CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
3) Measure the resistance of harness between
ECM and front oxygen (A/F) sensor connector.

Connector & terminal

(B135) No. 11 — (E24) No. 3:
(B135) No. 10 — (E24) No. 4:

Is the resistance less than 1

:? Go to step 4.

Repair the harness
and connector.

NOTE:
In this case, repair
the following item:
• Open circuit in
harness between
ECM and front oxy-
gen (A/F) sensor
connector
• Poor contact of
coupling connector

4

CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance between ECM and
chassis ground.

Connector & terminal

(B135) No. 11 — Chassis ground:
(B135) No. 10 — Chassis ground:

Is the resistance 1 M

: or

more?

Go to step 5.

Repair the ground
short circuit of har-
ness between
ECM and front oxy-
gen (A/F) sensor
connector.

5

CHECK OUTPUT SIGNAL FOR ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between front oxygen
(A/F) sensor connector and chassis ground.

Connector & terminal

(E24) No. 3 (+) — Chassis ground (–):

Is the voltage 4.5 V or more?

Go to step 7.

Go to step 6.

6

CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/F)
sensor connector and chassis ground.

Connector & terminal

(E24) No. 4 (+) — Chassis ground (–):

Is the voltage 4.95 V or more?

Go to step 7.

Go to step 8.

7

CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/F)
sensor connector and chassis ground.

Connector & terminal

(E24) No. 3 (+) — Chassis ground (–):
(E24) No. 4 (+) — Chassis ground (–):

Is the voltage 8 V or more?

Repair the short
circuit to power in
the harness
between ECM and
front oxygen (A/F)
sensor connector.
After repair,
replace the ECM.
<Ref. to
FU(H6DO)-38,
Engine Control
Module (ECM).>

Repair the poor
contact of ECM
connector.

8

CHECK EXHAUST SYSTEM.

Are there holes or loose bolts
on exhaust system?

Repair the exhaust
system.

Go to step 9.