Subaru Legacy III (2000-2003 year). Manual - part 498

EN(H4DOSTC)-162

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AI: DTC P0509 — IDLE CONTROL SYSTEM CIRCUIT HIGH —

• TROUBLE SYMPTOM:

• Erroneous idling
• Engine stalls.
• Engine breathing

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4DOSTC)-35, 
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOSTC)-33, Inspection 
Mode.> .
• WIRING DIAGRAM:

EN-00947

BATTERY

MAIN RELAY

E

E

6
4

5
3

2
1

10

       IDLE
AIR CONTROL
  SOLENOID
     VALVE

1

3

E7

B47

B47

3

4

1

2

5

6

1 2

7

8 9

5

6

3

4

10 11 12
19 20 21

13 14 15 16

17 18

22 23 24

B136

B136 ECM

2

1

B22

E3

SBF-5

B22

E7

1 2 3

1 2

5

6 7

8

13

14 15

16

9 10

11 12

3 4

17 18

19 20

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

B21

E2

B21

12

EN(H4DOSTC)-163

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK THROTTLE CABLE.
Does the throttle cable have play for adjust-
ment?

Cable has play correctly.

Go to step 2.

Adjust the throttle 
cable.  <Ref. to 
SP(H4SO)-10, 
Accelerator Con-
trol Cable.>

2

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

chassis 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 the ignition switch to OFF.
2) Disconnect the connector from idle air con-

trol solenoid valve.

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

chassis ground.

Connector & terminal

(B136) No. 10 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Repair the battery 
short circuit in har-
ness between 
ECM and idle air 
control solenoid 
valve connector. 
After repair, 
replace the ECM.  
<Ref. to 
FU(H4DOSTC)-
40, Engine Con-
trol Module.>

Replace the idle 
air control solenoid 
valve  <Ref. to 
FU(H4DOSTC)-
35, Idle Air Con-
trol Solenoid 
Valve.> and 
replace ECM 
<Ref. to 
FU(H4DOSTC)-
40, Engine Con-
trol Module.>.

4

CHECK OUTPUT SIGNAL FROM ECM.
Measure the voltage between ECM and chas-
sis ground.

Connector & terminal

(B136) No. 10 (+) — Chassis ground (

−−−−

):

Does the measured value change by shaking 
harness and connector of ECM while monitor-
ing the value with voltage meter?

The value changes.

Repair the battery 
short circuit in har-
ness between 
ECM and idle air 
control solenoid 
valve connector. 
After repair, 
replace the ECM.  
<Ref. to 
FU(H4DOSTC)-
40, Engine Con-
trol Module.>

Contact SUBARU 
distributor service.

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

EN(H4DOSTC)-164

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AJ:DTC P0512 — STARTER REQUEST CIRCUIT —

• TROUBLE SYMPTOM:

• Failure of engine to start

CAUTION:
After repair or replacement of faulty parts, conduct Clear Memory Mode <Ref. to EN(H4DOSTC)-35, 
OPERATION, Clear Memory Mode.> and Inspection Mode <Ref. to EN(H4DOSTC)-33, Inspection 
Mode.> .
• WIRING DIAGRAM:

EN-00930

BATTERY

IGNITION

SWITCH

STARTER
MOTOR

SBF-4

SBF-1

B72

B72

B14

B134 ECM

E

E

1

3

16

3 4

1 2

B134

B12

T7

1 2 3 4

10 11 12

19 20 21

13

5

6

14 15

7

8 9

16 17

18

22

12

INHIBITOR SWITCH

7

P

R

N

D

3

2

1

12

11

T7

T3

B12

AT

AT

MT

MT

1 2 3 4 5 6
7 8 9 10 11 12

1 2 3 4
5 6 7 8
9 10 11 12

EN(H4DOSTC)-165

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK OPERATION OF STARTER MOTOR.

NOTE:

Place the inhibitor switch in each position.

Does the starter motor operate when ignition 
switch to “ON”?

Operates.

Repair the battery 
short circuit in 
starter motor cir-
cuit. After repair, 
replace the ECM.  
<Ref. to 
FU(H4DOSTC)-
40, Engine Con-
trol Module.>

Check the starter 
motor circuit.  
<Ref. to 
EN(H4DOSTC)-
52, STARTER 
MOTOR CIR-
CUIT, Diagnostics 
for Engine Start-
ing Failure.>