Subaru Legacy III (2000-2003 year). Service manual — part 145

EN(H4SO)-192

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

5

CHECK OUTPUT SIGNAL FROM ECM.
1) Turn ignition switch to OFF.
2) Connect connectors to ECM and EGR sole-

noid valve.

3) Turn ignition switch to ON.
4) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B134) No. 15 — Chassis ground:
(B134) No. 16 — Chassis ground:
(B134) No. 17 — Chassis ground:
(B134) No. 18 — Chassis ground:

Does the measured value change within
specified range?

0 — 10 V

Repair poor con-
tact in ECM con-
nector.

Go to step 6.

6

CHECK HARNESS BETWEEN EGR SOLE-
NOID VALVE AND ECM CONNECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connectors from EGR solenoid

valve and ECM.

3) Measure resistance of harness between

EGR solenoid valve and ECM connector.

Connector & terminal

(B134) No. 18 — (E18) No. 6:
(B134) No. 17 — (E18) No. 1:
(B134) No. 16 — (E18) No. 4:
(B134) No. 15 — (E18) No. 3:

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

1

Ω

Go to step 7.

Repair open circuit
in harness
between ECM and
EGR solenoid
valve connector.

7

CHECK HARNESS BETWEEN EGR SOLE-
NOID VALVE AND ECM CONNECTOR.
Measure resistance of harness between EGR
solenoid valve and chassis ground.

Connector & terminal

(B134) No. 18 — Chassis ground:
(B134) No. 17 — Chassis ground:
(B134) No. 16 — Chassis ground:
(B134) No. 15 — Chassis ground:

Does the measured value exceed the specified
value?

1 M

Ω

Go to step 8.

Repair short circuit
in harness
between main
relay and EGR
solenoid valve
connector.

8

CHECK POOR CONTACT.
Check poor contact in ECM and EGR solenoid
valve connector.
Is there poor contact in ECM and EGR sole-
noid valve connector?

There is poor contact.

Repair poor con-
tact in ECM and
EGR solenoid
valve connector.

Even if MI lights
up, the circuit has
returned to a nor-
mal condition at
this time.

Step

Value

Yes

No

EN(H4SO)-193

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO:

EN(H4SO)-194

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AN:DTC P0420 — CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD

(BANK 1) —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

• TROUBLE SYMPTOM:

• Engine stalls.
• Idle mixture is out of specifications.

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode<Ref. to EN(H4SO)-47, OPER-
ATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4SO)-40, OPERATION, Inspection
Mode.> .
• WIRING DIAGRAM:

EN-01130

F44

B61

6

RHD

RHD

BATTERY

B47

MAIN RELAY

1

2

3

5

4

6

F44

1 2 3 4
5 6 7 8

4

C6

C17

C22

C13

B23

2

3

2

1

FRONT OXYGEN

(A/F) SENSOR

B19

B14

C4

D15

REAR

OXYGEN

SENSOR

4

3

1

1

3

4

B19

T5

B18

T6

ECM

B136

C:

B135

B:

B137

D:

B47

3

4

1

2

5

6

T5

B19

2

B83

T6

B19

1

2

3

4

SBF-5

B18

B83

1 2 3 4 5 6

B136

5 6

7

2

1

9

8

4

3

23

21 22

24

10 11 12 13 14

25 26

15 16 17

18 19 20

B137

4

1
5

3

2
6

18

15

16

7 8 9 10 11

17

19 20

12 13

14

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

B135

4

2 1

3

LHD

LHD

2

1

FG

3

4

EG

: FOR G.C.C COUNTRIES
MODEL

: EXCEPT FOR G.C.C
COUNTRIES MODEL

FG

EG

EN(H4SO)-195

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?

DTC indicated.

Inspect the rele-
vant DTC using
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(H4SO)-83, List
of Diagnostic
Trouble Code
(DTC).>

NOTE:
In this case, it is
not necessary to
inspect DTC
P0420.

Go to step 2.

2

CHECK EXHAUST SYSTEM.
Check for gas leaks or air suction caused by
loose or dislocated nuts and bolts, and open
hole at exhaust pipes.
Is there any fault in exhaust system?

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 cat-
alytic converter

There is a fault.

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

Go to step 3.

3

CHECK CATALYTIC CONVERTER.
Is there any damage at catalyst?

There is a damage.

Replace front cat-
alytic converter.
<Ref. to
EC(H4SO)-3,
Front Catalytic
Converter.>

Go to step 4.

4

CHECK REAR OXYGEN SENSOR CIRCUIT.
1) Disconnect rear oxygen sensor connector.
2) Measure the resistance between ECM and

rear oxygen sensor connector.

Connector & terminal

(B135) No. 19 - (T6) No. 3

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

1

Ω

Go to step 5.

Repair open har-
ness between
ECM and rear oxy-
gen sensor.

5

CHECK SEALED WIRE.
Is the sealed wire connected?

Connected.

Contact SUBARU
distributor service.

NOTE:
Inspection by DTM
is required, be-
cause probable
cause is deteriora-
tion of multiple
parts.

Repair sealed
wire.