Subaru Legacy III (2000-2003 year). Manual - part 484

EN(H4DOSTC)-106

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

6

CHECK HARNESS BETWEEN ECM AND 
THROTTLE POSITION SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from throttle 

position sensor.

3) Turn the ignition switch to ON.
4) Measure the voltage between throttle posi-

tion sensor connector and engine ground.

Connector & terminal

(E13) No. 1 (+) — Engine ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

4.5 V

Go to step 7.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
throttle position 
sensor and ECM 
connector
• Poor contact in 
throttle position 
sensor connector
• Poor contact in 
ECM connector
• Poor contact in 
coupling connector
• Poor contact in 
joint connector

7

CHECK HARNESS BETWEEN ECM AND 
THROTTLE POSITION SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness 

between ECM connector and throttle posi-
tion sensor connector.

Connector & terminal

(B135) No. 7 — (E13) No. 3:

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

1 

Ω

Go to step 8.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
throttle position 
sensor and ECM 
connector
• Poor contact in 
ECM connector
• Poor contact in 
throttle position 
sensor connector
• Poor contact in 
coupling connector

8

CHECK HARNESS BETWEEN ECM AND 
THROTTLE POSITION SENSOR CONNEC-
TOR.
Measure the resistance of harness between 
throttle position sensor connector and engine 
ground.

Connector & terminal

(E13) No. 3 — Engine ground:

Does the measured value exceed the specified 
value?

1 M

Ω

Go to step 9.

Repair the ground 
short circuit in har-
ness between 
throttle position 
sensor and ECM 
connector.

9

CHECK POOR CONTACT.
Check the poor contact in throttle position sen-
sor connector. 
Is there poor contact in throttle position sensor 
connector?

There is poor contact.

Repair the poor 
contact in throttle 
position sensor 
connector.

Replace the throt-
tle position sensor.  
<Ref. to 
FU(H4DOSTC)-
32, Throttle Posi-
tion Sensor.>

Step

Value

Yes

No

EN(H4DOSTC)-107

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO:

EN(H4DOSTC)-108

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

N: DTC P0123 — THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT 

HIGH INPUT —

• TROUBLE SYMPTOM:

• Erroneous idling
• Engine stalls.
• 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-00937

E2

E13

B21

B122

THROTTLE
 POSITION
  SENSOR

1

3

2

20

19

18

6

1

B135 ECM

9

19

7

B135

5 6

7 8

2

1

9

4

3

10

24

22

23

25

11 12 13 14 15

26 27 28

16 17 18 19

20 21

E13

1 2 3

B21

1 2

5

6 7

8

13

14 15

16

9 10

11 12

3 4

17 18

19 20

B122

1 2 3 4 5 6

EN(H4DOSTC)-109

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of throttle position sensor 

signal using Subaru Select Monitor.
Does the measured value exceed the spec-
ified value?

NOTE:

For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOSTC)-26, Subaru Select Monitor.>  

4.7 V

Go to step 2.

Even if MI lights 
up, the circuit has 
returned to a nor-
mal condition at 
this time. A tempo-
rary poor contact 
of the connector 
may be the cause.

NOTE:
In this case, repair
the following:
• Poor contact in 
throttle position 
sensor connector
• Poor contact in 
ECM connector
• Poor contact in 
coupling connector

2

CHECK HARNESS BETWEEN THROTTLE 
POSITION SENSOR AND ECM CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from throttle posi-

tion sensor.

3) Measure the resistance of harness 

between throttle position sensor connector 
and engine ground.

Connector & terminal

(E13) No. 2 — Engine ground:

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

5 

Ω

Go to step 3.

Repair the har-
ness and connec-
tor.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
throttle position 
sensor and ECM 
connector
• Poor contact in 
coupling connector
• Poor contact in 
joint connector

3

CHECK HARNESS BETWEEN THROTTLE 
POSITION SENSOR AND ECM CONNEC-
TOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between throttle posi-

tion sensor connector and engine ground.

Connector & terminal

(E13) No. 3 (+) — Engine ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

4.7 V

Repair the battery 
short circuit in har-
ness between 
throttle position 
sensor and ECM 
connector. After 
repair, replace the 
ECM.  <Ref. to 
FU(H4DOSTC)-
40, Engine Con-
trol Module.>

Replace the throt-
tle position sensor.  
<Ref. to 
FU(H4DOSTC)-
32, Throttle Posi-
tion Sensor.>