Subaru Legacy III (2000-2003 year). Manual — part 378

EN(H6DO)-314

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

CL: DTC P1154 — O2 SENSOR CIRCUIT RANGE/PERFORMANCE (LOW) (BANK

2 SENSOR 1) —

NOTE:
For the diagnostic procedure, refer to DTC P1155. <Ref. to EN(H6DO)-314, DTC P1155 — O2 SENSOR
CIRCUIT RANGE/PERFORMANCE (HIGH) (BANK 2 SENSOR 1) —, Diagnostic Procedure with Diagnostic
Trouble Code (DTC).>

CM:DTC P1155 — O2 SENSOR CIRCUIT RANGE/PERFORMANCE (HIGH)

(BANK 2 SENSOR 1) —

• 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.>.

EN(H6DO)-315

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

• WIRING DIAGRAM:

EN-01087

BATTERY

F44

B61

SBF-5

6

B47

MAIN RELAY

1

2

3

5

4

6

9

8

21

31

2

1

5

B252

E49

ECM

18

29

19

5

4

7

6

20

30

4

1

3

FRONT

OXYGEN

(A/F)

SENSOR RH

E47

2

4

3

1

FRONT

OXYGEN

(A/F)

SENSOR LH

E24

B137

E3

B22

B83

11

8

1

2

3

E2

B21

2

3

E2

B21

20

19

E49

B252

4

8

LHD

RHD

LHD

RHD

B252

B47

3

4

5

6

1

2

E24

E47

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

1 2 3 4
5 6 7 8

3

4

1

2

1 2 3 4
5 6 7 8

F44

B21

1 2

5

6 7

8

13

14 15

16

9 10

11 12

3 4

17 18

19 20

B83

1 2 3 4

5 6 7 8 9 10

11 12

19

20

13 14 15 16 17 18

EN(H6DO)-316

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

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

Another DTC is displayed.

Inspect the rele-
vant DTC using
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(H6DO)-89, List
of Diagnostic
Trouble Code
(DTC).>

Go to step 2.

2

CHECK FRONT (A/F) OXYGEN SENSOR DA-
TA.
1) Start engine.
2) While observing the Subaru Select Monitor

or OBD-II general scan tool screen, warm-
up the engine until coolant temperature is
above 75

°

C (167

°

F).

If the engine is already warmed-up, operate
at idle speed for at least 1 minute.

3) Read data of front oxygen (A/F) sensor sig-

nal using Subaru Select Monitor or OBD-II
general scan tool.
Is the measured value within the specified
range at idle?

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 procedures, refer to the
OBD-II General Scan Tool Instruction Manual.

0.85 — 1.15

Go to step 3.

Go to step 4.

3

CHECK REAR OXYGEN SENSOR SIGNAL.
1) Race engine at speeds from idling to 5,000

rpm for a total of 5 cycles.

NOTE:

To increase engine speed to 5,000 rpm, slowly
depress accelerator pedal, taking approximate-
ly 5 seconds, and quickly release accelerator
pedal to decrease engine speed.

2) Operate the LED operation mode for

engine.
Does the LED of {Rear O2 Rich Signal}
blink?

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to the
“LED OPERATION MODE FOR ENGINE”.
<Ref. to EN(H6DO)-34, Subaru Select Moni-
tor.>

LED blinks.

Repair poor con-
tact in front oxygen
(A/F) sensor and
rear oxygen sen-
sor connector.

Check rear oxygen
sensor circuit.
<Ref. to
FU(H6DO)-45,
Rear Oxygen Sen-
sor.>

EN(H6DO)-317

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

4

CHECK EXHAUST SYSTEM.
Check exhaust system parts.

NOTE:

Check the following items.
• Loose installation of portions
• Damage (crack, hole etc.) of parts
• Looseness of front oxygen (A/F) sensor
• Looseness and ill fitting of parts between
front oxygen (A/F) sensor and rear oxygen
sensor

Is there a fault in exhaust system?

There is a malfunction.

Repair or replace
faulty parts.

Replace front oxy-
gen (A/F) sensor.
<Ref. to
FU(H6DO)-43,
Front Oxygen (A/
F) Sensor.>

Step

Value

Yes

No