Subaru Legacy III (2000-2003 year). Manual - part 364

EN(H6DO)-258

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

BJ:DTC P0508 — IDLE CONTROL SYSTEM CIRCUIT LOW —

• DTC DETECTING CONDITION:

• Immediately at fault recognition

• TROUBLE SYMPTOM:

• Erroneous idling
• Engine stalls.
• Engine breathing

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-01094

C17

C10

A22

B20

E1

ECM

2

3

1

9

3

IDLE 

AIR CONTROL

SOLENOID 

VALVE

E7

B20

E1

B47

B134

A:

B136

C:

B47

3

4

1

2

5

6

B134

B20

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

E7

B136

SBF-5

BATTERY

MAIN RELAY

1

2

3

5

4

6

4

F46

3 4

1 2

1 2 3

1 2

7

8 9

5

6

3

4

10 11 12
19 20 21

13 14 15 16

17 18

22 23 24

1 2 3 4

10 11 12

19 20 21

13

5

6

14 15

7

8 9

16 17

18

22

2

B108

F46

RHD

LHD

LHD

RHD

EN(H6DO)-259

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK OUTPUT SIGNAL FROM ECM.
1) Turn ignition switch to ON.
2) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B136) No. 10 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

3 V

Repair poor con-
tact in ECM con-
nector.

Go to step 2.

2

CHECK POWER SUPPLY TO IDLE AIR CON-
TROL SOLENOID VALVE.
1) Turn ignition switch to OFF.
2) Disconnect connector from idle air control 

solenoid valve.

3) Turn ignition switch to ON.
4) Measure voltage between idle air control 

solenoid valve and engine ground.

Connector & terminal

(E7) No. 2 (+) — Engine ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 3.

Repair harness 
and connector.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
idle air control 
solenoid valve and 
main relay con-
nector
• Poor contact in 
coupling connector

3

CHECK HARNESS BETWEEN ECM AND 
IDLE AIR CONTROL SOLENOID VALVE 
CONNECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM.
3) Measure resistance of harness between 

ECM and idle air control solenoid valve 
connector.

Connector & terminal

(B136) No. 10 — (E7) No. 1:

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

1 

Ω

Go to step 4.

Repair harness 
and connector.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
ECM and idle air 
control solenoid 
valve connector
• Poor contact in 
coupling connector

4

CHECK HARNESS BETWEEN ECM AND 
IDLE AIR CONTROL SOLENOID VALVE 
CONNECTOR.
Measure resistance of harness between ECM 
and chassis ground.

Connector & terminal

(B136) No. 10 — Chassis ground:

Is the measured value less than the specified 
value?

10 

Ω

Repair ground 
short circuit in har-
ness between 
ECM and idle air 
control solenoid 
valve connector.

Go to step 5.

5

CHECK GROUND CIRCUIT OF IDLE AIR 
CONTROL SOLENOID VALVE.
Measure resistance of harness between idle 
air control solenoid valve connector and 
engine ground.

Connector & terminal

(E7) No. 3 — Engine ground:

Is the measured value less than the specified 
value?

5 

Ω

Go to step 6.

Repair open circuit 
in harness 
between idle air 
control solenoid 
valve connector 
and engine ground 
terminal.

6

CHECK POOR CONTACT.
Check poor contact in ECM and idle air control 
solenoid valve connectors. 
Is there poor contact in ECM and idle air con-
trol solenoid valve connectors?

There is poor contact.

Repair poor con-
tact in ECM and 
idle air control 
solenoid valve 
connectors.

Replace idle air 
control solenoid 
valve. <Ref. to 
FU(H6DO)-36, Idle 
Air Control Sole-
noid Valve.>

EN(H6DO)-260

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

BK:DTC P0509 — IDLE CONTROL SYSTEM CIRCUIT HIGH —

• DTC DETECTING CONDITION:

• Immediately at fault recognition

• TROUBLE SYMPTOM:

• Erroneous idling
• Engine stalls.
• Engine breathing

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-01094

C17

C10

A22

B20

E1

ECM

2

3

1

9

3

IDLE 

AIR CONTROL

SOLENOID 

VALVE

E7

B20

E1

B47

B134

A:

B136

C:

B47

3

4

1

2

5

6

B134

B20

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

E7

B136

SBF-5

BATTERY

MAIN RELAY

1

2

3

5

4

6

4

F46

3 4

1 2

1 2 3

1 2

7

8 9

5

6

3

4

10 11 12
19 20 21

13 14 15 16

17 18

22 23 24

1 2 3 4

10 11 12

19 20 21

13

5

6

14 15

7

8 9

16 17

18

22

2

B108

F46

RHD

LHD

LHD

RHD

EN(H6DO)-261

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK THROTTLE CABLE.
Does throttle cable have play for adjustment?

Throttle cable has play for 
adjustment.

Go to step 2.

Adjust throttle 
cable. <Ref. to 
SP(H6DO)-8, 
Accelerator Con-
trol Cable.>

2

CHECK OUTPUT SIGNAL FROM ECM.
1) Turn ignition switch to ON.
2) Measure voltage between ECM and chas-

sis ground.

Connector & terminal

(B136) No. 10 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 3.

Go to step 4.

3

CHECK OUTPUT SIGNAL FROM ECM.
1) Turn ignition switch to OFF.
2) Disconnect connector from idle air control 

solenoid valve.

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

sis ground.

Connector & terminal

(B136) No. 10 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Repair battery 
short circuit in har-
ness between 
ECM and idle air 
control solenoid 
valve connector. 
After repair, 
replace ECM. 
<Ref. to 
FU(H6DO)-46, 
Engine Control 
Module.>

Replace idle air 
control solenoid 
valve <Ref. to 
FU(H6DO)-36, Idle 
Air Control Sole-
noid Valve.> and 
ECM <Ref. to 
FU(H6DO)-46, 
Engine Control 
Module.>.

4

CHECK OUTPUT SIGNAL FROM ECM.
Measure voltage between ECM and chassis 
ground.

Connector & terminal

(B136) No. 10 (+) — Chassis ground (

−−−−

):

Does the voltage change exceed the specified 
value by shaking harness and connector of 
ECM while monitoring the value with voltage 
meter?

10 V

Repair battery 
short circuit in har-
ness between 
ECM and idle air 
control solenoid 
valve connector. 
After repair, 
replace ECM. 
<Ref. to 
FU(H6DO)-46, 
Engine Control 
Module.>

Contact SUBARU 
distributor service.

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