Subaru Legacy III (2000-2003 year). Manual — part 356

EN(H6DO)-226

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AX:DTC P0400 — EXHAUST GAS RECIRCULATION FLOW —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

• TROUBLE SYMPTOM:

• Poor driving performance on low engine speed
• Erroneous idling
• Poor driving performance.

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.>.

• WIRING DIAGRAM:

EN-01090

F46

B47

4

3

1

6

2

4

6

12

26

25

14

13

B20

E1

B108

F46

E1

B20

E18

5

2

1

5

B137 ECM

EGR

SOLENOID

VALVE

BATTERY

SBF-5

B47

MAIN RELAY

1

2

3

5

4

6

B20

E18

1

3

4 5 6

2

3 4

1 2

3

4

1

2

5

6

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
9 10 11 12

13 14 15 16

LHD

RHD

LHD

RHD

EN(H6DO)-227

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 CURRENT DATA.
1) Start engine.
2) Rear the data of intake manifold absolute

pressure signal using Subaru Select Moni-
tor or OBD-II general scan tool.
Does the measured value exceed the spec-
ified value?

NOTE:

• Subaru Select Monitor
<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.

53.3 kPa (400 mmHg, 15.75
inHg)

Check if EGR
valve, intake mani-
fold pressure sen-
sor and throttle
body are securely
installed.

Go to step 3.

3

CHECK POWER SUPPLY TO EGR SOLE-
NOID VALVE.
1) Disconnect connector from EGR solenoid

valve.

2) Turn ignition switch to ON.
3) Measure voltage between EGR solenoid

valve and engine ground.

Connector & terminal

(E18) No. 2 — Engine ground:
(E18) No. 5 — Engine ground:

Does the measured value exceed the spec-
ified value?

10 V

Go to step 4.

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

4

CHECK EGR SOLENOID VALVE.
Measure resistance between EGR solenoid
valve terminals.

NOTE:

Make sure there are no foreign objects caught
between EGR solenoid valve and valve seat.

Terminals

No. 1 — No. 2:
No. 3 — No. 2:
No. 4 — No. 5:
No. 6 — No. 5:

Is the measured value within the specified
range?

20 — 30

Ω

Go to step 5.

Replace EGR
solenoid valve.
<Ref. to
EC(H6DO)-10,
EGR Valve.>

EN(H6DO)-228

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

(B137) No. 25 — Chassis ground:
(B137) No. 26 — Chassis ground:
(B137) No. 13 — Chassis ground:
(B137) No. 14 — Chassis ground:

Does the measured value fluctuate within
the 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

(B137) No. 25 — (E18) No. 6:
(B137) No. 26 — (E18) No. 1:
(B137) No. 13 — (E18) No. 4:
(B137) No. 14 — (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

(B137) No. 25 — Chassis ground:
(B137) No. 26 — Chassis ground:
(B137) No. 13 — Chassis ground:
(B137) No. 14 — 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(H6DO)-229

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO: