Subaru Legacy III (2000-2003 year). Manual - part 507

EN(H4DOSTC)-198

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AX:DTC P1235 — INTAKE CONTROL SOLENOID VALVE CIRCUIT LOW —

• TROUBLE SYMPTOM:

• Poor driving performance

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-00939

B220

B47

E

BATTERY

MAIN RELAY

3

B136

ECM

SBF-5

5

2
1

4

6

B47

3

4

1

2

5

6

B220

SOLENOID 
BOX ASSY

1

2

3

4

5

6

7

8

9

10

11

12

(A)

(B)

(C)

(D)

(E)

(F)

(A): RELIEF VALVE SOLENOID 2
(B): RELIEF VALVE SOLENOID 1
(C): EXHAUST VALVE CONTROL SOLENOID VALVE
       (NEGATIVE PRESSURE)
(D): EXHAUST VALVE CONTROL SOLENOID VALVE
       (POSITIVE PRESSURE)
(E): INTAKE AIR CONTROL SOLENOID VALVE
(F): EXHAUST VALVE CONTROL DUTY SOLENOID VALVE

C:

B137

D:

C11

C12

C3

C1

D22

D11

1 2 3 4
5 6 7 8
9 10 11 12

B136

1 2

7

8 9

5

6

3

4

10 11 12
19 20 21

13 14 15 16

17 18

22 23 24

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

EN(H4DOSTC)-199

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

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

chassis ground.

Connector & terminal

(B137) No. 22 (+) — Chassis ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

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

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

Go to step 2.

2

CHECK HARNESS BETWEEN INTAKE AIR 
VALVE CONTROL SOLENOID VALVE AND 
ECM CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from intake air 

valve control solenoid valve and ECM.

3) Measure the resistance of harness 

between intake air valve control solenoid 
valve connector and engine ground.

Connector & terminal

(B220) No. 10 — Engine ground:

Does the measured value exceed the spec-
ified value?

1 M

Ω

Go to step 3.

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

3

CHECK HARNESS BETWEEN INTAKE AIR 
VALVE CONTROL SOLENOID VALVE AND 
ECM CONNECTOR.
Measure the resistance of harness between 
ECM and intake air valve control solenoid 
valve of harness connector.

Connector & terminal

(B137) No. 22 — (B220) No. 10:

Is the measured value less than the specified 
value?

1 

Ω

Go to step 4.

Repair the open 
circuit in harness 
between ECM and 
intake air valve 
control solenoid 
valve connector.

4

CHECK INTAKE AIR VALVE CONTROL SO-
LENOID VALVE.
Measure the resistance between intake air 
valve control solenoid valve terminals.

Terminals

No. 9 — No. 10:

Is the measured value within the specified 
value?

37 — 44 

Ω

Go to step 5.

Replace the intake 
air valve control 
solenoid valve.  
<Ref. to 
IN(H4DOSTC)-19, 
Solenoid Box 
Assembly.>

5

CHECK POWER SUPPLY TO INTAKE AIR 
VALVE CONTROL SOLENOID VALVE.
1) Turn the ignition switch to ON.
2) Measure the voltage between intake air 

valve control solenoid valve and engine 
ground.

Connector & terminal

(B220) No. 9 (+) — Engine ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Go to step 6.

Repair the open 
circuit in harness 
between main 
relay and intake air 
valve control sole-
noid valve connec-
tor.

EN(H4DOSTC)-200

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

6

CHECK POOR CONTACT.
Check poor contact in intake air valve control 
solenoid valve and ECM connectors.
Is there poor contact in intake air valve control 
solenoid valve and ECM connectors?

There is poor contact.

Repair the poor 
contact in intake 
air valve control 
solenoid valve and 
ECM connectors.

Contact SUBARU 
distributor service.

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

Step

Value

Yes

No

EN(H4DOSTC)-201

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO: