Subaru Legacy IV (2008 year). Service manual — part 148

EN(H4SO)(diag)-195

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK EXHAUST SYSTEM.
Check for gas leaks or air suction caused by
loose or dislocated nuts and bolts, and open
hole at exhaust pipes.

NOTE:
Check the following positions.
• Between cylinder head and front exhaust
pipe
• Between front exhaust pipe and front catalytic
converter
• Between front catalytic converter and rear
catalytic converter
• Looseness and improper attachment of front
oxygen (A/F) sensor or rear oxygen sensor

Is there any fault in exhaust
system?

Repair or replace
the exhaust sys-
tem. <Ref. to
EX(H4SO)-2, Gen-
eral Description.>

Go to step 2.

2

CHECK WAVEFORM DATA ON THE SUBA-
RU SELECT MONITOR (WHILE DRIVING).
1) Drive at a constant speed between 80 —
112 km/h (50 — 70 MPH).
2) After 5 minutes have elapsed in the condi-
tion of step 1), use the Subaru Select Monitor
while still driving to read the waveform data.
• At normal condition

• At abnormal condition (numerous inversion)

Is normal waveform pattern dis-
played?

Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.

NOTE:
In this case, tem-
porary poor con-
tact of connector
may be the cause.

Go to step 3.

EN-06666

1

0

1.5

0.5

10 sec/div

REAR OXYGEN
SENSOR VOLTAGE
(V)

A/F SENSOR
OUTPUT LAMBDA 1

EN-06667

1

0

1.5

0.5

10 sec/div

REAR OXYGEN
SENSOR VOLTAGE
(V)

A/F SENSOR
OUTPUT LAMBDA 1

EN(H4SO)(diag)-196

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

3

CHECK WAVEFORM DATA ON THE SUBA-
RU SELECT MONITOR (WHILE IDLING).
1) Run the engine at idle.
2) In the condition of step 1), use the Subaru
Select Monitor to read the waveform data.
• At normal condition

• At abnormal condition 1 (numerous inversion)

• At abnormal condition 2 (noise input)

Is normal waveform pattern dis-
played?

Go to step 4.

• The waveform is
displayed at abnor-
mal condition 1:Go
to step 4.
• The waveform is
displayed at abnor-
mal condition 2:Go
to step 5.

4

CHECK CATALYTIC CONVERTER.

Is the catalytic converter dam-
aged?

Replace the cata-
lytic converter.
<Ref. to
EC(H4SO)-3,
Front Catalytic
Converter.>

Go to step 5.

5

CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.

Has water entered the connec-
tor?

Completely
remove any water
inside.

Go to step 6.

Step

Check

Yes

No

EN-06668

1

0

10 sec/div

REAR OXYGEN
SENSOR VOLTAGE
(V)

EN-06669

1

0

10 sec/div

REAR OXYGEN
SENSOR VOLTAGE
(V)

EN-06670

1

0

10 sec/div

REAR OXYGEN
SENSOR VOLTAGE
(V)

EN(H4SO)(diag)-197

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

6

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 — (E23) No. 3:
(B134) No. 29 — (E23) No. 4:

Is the resistance less than 1

:? Go to step 7.

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

7

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

Connector & terminal

(E23) No. 3 (+) — Chassis ground (–):

Is the voltage 0.2 — 0.5 V?

Go to step 8.

Repair the harness
and connector.

NOTE:
Repair the follow-
ing locations.
• Open circuit in
harness between
ECM and rear oxy-
gen sensor con-
nector
• Poor contact in
ECM and rear oxy-
gen sensor
• Poor contact in
ECM connector

8

CHECK REAR OXYGEN SENSOR SHIELD.
1) Turn the ignition switch to OFF.
2) Expose the rear oxygen sensor connector
body side harness sensor shield.
3) Measure the resistance between the sensor
shield and chassis ground.

Is the resistance less than 1

:? Replace the rear

oxygen sensor.
<Ref. to
FU(H4SO)-37,
Rear Oxygen Sen-
sor.>

Repair the open
circuit in the rear
oxygen sensor har-
ness.

Step

Check

Yes

No

EN(H4SO)(diag)-198

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

BF:DTC P0442 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECTED

(SMALL LEAK)

DTC DETECTING CONDITION:
• Two consecutive driving cycles with fault
• GENERAL DESCRIPTION <Ref. to GD(H4SO)-101, DTC P0442 EVAPORATIVE EMISSION CONTROL
SYSTEM LEAK DETECTED (SMALL LEAK), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Fuel odor
• There is a hole of more than 1.0 mm (0.04 in) dia. in evaporation system or fuel tank.

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4SO)(diag)-50,
OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4SO)(diag)-41, PROCEDURE,
Inspection Mode.>.
WIRING DIAGRAM:

EN-06840

5
3

6
4

2
1

B47

SBF-7

E4

1

2

E2

B21

41

48

D29

R68

1

2

R213

R15

1

5

R1

B97

14

15

R67

R46

7

6

C17

C28

R144

1

2

B136

C:

B137

D:

3

1

2

4

5

6

B47

R213

E

PURGE CONTROL

SOLENOID VALVE

ECM

DRAIN VALVE

PRESSURE CONTROL

SOLENOID VALVE

MAIN RELAY

BATTERY

B21

E4

1 2

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

1 2

3

4 5 6 7 8

1 2

R68

1 2

B97

R144

R67

1

2

3 4 5 6

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:

B137

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

D:

1 2 3 4

5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20