Subaru Legacy III (2000-2003 year). Manual - part 153

EN(H4SO)-224

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK TRANSMISSION TYPE.
Is the transmission type AT?

Transmission type is AT.

Go to step 2.

Go to step 3.

2

CHECK DTC P0720 ON DISPLAY.
Does the Subaru Select Monitor or OBD-II 
general scan tool indicate DTC P0720?

DTC P0720 indicated.

Check front vehi-
cle speed sensor 
signal circuit.  
<Ref. to AT-58, 
DTC 33 FRONT 
VEHICLE SPEED 
SENSOR, Diag-
nostic Procedure 
with Diagnostic 
Trouble Code 
(DTC).>

Go to step 3.

3

CHECK SPEEDOMETER OPERATION IN 
COMBINATION METER.
Does speedometer operate normally?

Operates normally.

Go to step 4.

Check speedome-
ter and vehicle 
speed sensor. 
<Ref. to IDI-18, 
Speedometer.> 
and  <Ref. to AT-
54, Front Vehicle 
Speed Sensor.> 
and <Ref. to AT-
58, Rear Vehicle 
Speed Sensor.> 
and  <Ref. to AT-
59, Torque Con-
verter Turbine 
Speed Sensor.>

4

CHECK HARNESS BETWEEN ECM AND 
COMBINATION METER CONNECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from combination 

meter.

3) Measure resistance between ECM and 

combination meter.

Connector & terminal

(B137) No. 10 — (i10) No. 13:

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

10 

Ω

Repair poor con-
tact in ECM con-
nector.

Repair harness 
and connector.

NOTE:
In this case, repair
the following:

• Open circuit in 
harness between 
ECM and combi-
nation meter con-
nector
• Poor contact in 
ECM connector
• Poor contact in 
combination meter 
connector
• Poor contact in 
coupling connector

EN(H4SO)-225

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO:

EN(H4SO)-226

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

AX:DTC P0506 — IDLE CONTROL SYSTEM RPM LOWER THAN EXPECTED —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

• TROUBLE SYMPTOM:

• Engine is difficult to start.
• Engine does not start.
• Erroneous idling
• Engine stalls.

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-01134

F44

B61

6

RHD

RHD

20

6

5

19

B21

E2

ECM

2

5

6

3

4

1

3

4

1

2

IDLE 

AIR CONTROL

SOLENOID 

VALVE

E7

B22

E3

B47

B134

B47

3

4

1

2

5

6

B134

1 2

3 4

5 6

7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

24 25

26 27 28 29

30 31 32 33

34 35

B22

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

E7

1

3

4 5 6

2

B21

1 2

3 4

5

6 7

8

9 10

11 12

13

14 15

16

17 18

19 20

SBF-5

BATTERY

MAIN RELAY

1

2

3

5

4

6

1

1 2 3 4
5 6 7 8

F44

LHD

LHD

EN(H4SO)-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?

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
P0506.

Go to step 2.

2

CHECK AIR BY-PASS LINE.
1) Turn ignition switch to OFF.
2) Remove idle air control solenoid valve from 

throttle body. <Ref. to FU(H4SO)-34, 
REMOVAL, Idle Air Control Solenoid 
Valve.>

3) Remove throttle body from intake manifold. 

<Ref. to FU(H4SO)-14, REMOVAL, Throt-
tle Body.>

4) Using an air gun, force air into idle air con-

trol solenoid valve installation area. Confirm 
that forced air subsequently escapes from 
throttle body interior.
Does air flow out?

Flows out.

Replace idle air 
control solenoid 
valve. <Ref. to 
FU(H4SO)-34, 
INSTALLATION, 
Idle Air Control 
Solenoid Valve.>

Replace throttle 
body. <Ref. to 
FU(H4SO)-14, 
INSTALLATION, 
Throttle Body.>