Subaru Legacy III (2000-2003 year). Manual - part 338

EN(H6DO)-154

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

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

HIGH INPUT —

• DTC DETECTING CONDITION:

• Immediately at fault recognition

• TROUBLE SYMPTOM:

• Erroneous idling
• Engine stalls.
• Poor driving performance

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-00814

19

7

9

13

15

16

1

2

3

E1

B20

E13

THROTTLE

POSITION

SENSOR

E13

1 2 3

5

8

B83

B20

B135

ECM

B83

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

1 2 3 4
5 6 7 8
9 10 11 12

13 14 15 16

1 2 3 4

5 6 7 8 9 10

11 12

19 20

13 14 15 16 17 18

EN(H6DO)-155

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

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

using Subaru Select Monitor or OBD-II gen-
eral scan tool.
Does the measured value exceed the spec-
ified value?

NOTE:

• Subaru Select Monitor
For detailed operation procedure, refer to the 
“READ CURRENT DATA FOR ENGINE”. 
<Ref. to EN(H6DO)-34, Subaru Select Moni-
tor.>  
• OBD-II general scan tool
For detailed operation procedures, refer to the 
OBD-II General Scan Tool Instruction Manual.

4.75 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 ignition switch to OFF.
2) Disconnect connector from throttle position 

sensor.

3) Measure 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 harness 
and connector.

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 ignition switch to ON.
2) Measure voltage between throttle position 

sensor connector and engine ground.

Connector & terminal

(E13) No. 3 (+) — Engine ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

4.9 V

Repair battery 
short circuit in har-
ness between 
throttle position 
sensor and ECM 
connector. After 
repair, replace 
ECM. <Ref. to 
FU(H6DO)-46, 
Engine Control 
Module.>

Replace throttle 
position sensor. 
<Ref. to 
FU(H6DO)-33, 
Throttle Position 
Sensor.>

EN(H6DO)-156

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

T: DTC P0125 — INSUFFICIENT COOLANT TEMPERATURE FOR CLOSED 

LOOP FUEL CONTROL —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

• TROUBLE SYMPTOM:

• Engine does not return to idle.

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-00813

19

18

12

5

B135 ECM

2

1

E2

B21

E8

ENGINE

COOLANT

TEMPERATURE 

SENSOR

E8

5

6

B83

B21

1 2

3 4

5

6 7

8

9 10

11 12

13

14 15

16

17 18

19 20

1 2

3

B83

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

1 2 3 4

5 6 7 8 9 10

11 12

19 20

13 14 15 16 17 18

EN(H6DO)-157

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?

Another DTC is displayed.

Inspect the rele-
vant DTC using 
“List of Diagnostic 
Trouble Code 
(DTC)”. <Ref. to 
EN(H6DO)-89, List 
of Diagnostic 
Trouble Code 
(DTC).>

NOTE:
In this case, it is
not necessary to
inspect DTC
P0125.

Go to step 2.

2

CHECK TIRE SIZE.
Is the tire size the same as designated tire and 
four-wheel tire?

Same.

Go to step 3.

Replace tire.

3

CHECK ENGINE COOLANT.
Check the following items.
• Engine coolant volume
• Engine coolant freezing
• Contamination in engine coolant
Is the engine coolant normal?

Normal.

Go to step 4.

Refill or replace 
coolant. <Ref. to 
CO(H6DO)-23, 
INSPECTION, 
Engine Coolant.>

4

CHECK THERMOSTAT.
Does thermostat remain open?

Remains open.

Replace thermo-
stat. <Ref. to 
CO(H6DO)-25, 
Thermostat.>

Replace engine 
coolant tempera-
ture sensor. <Ref. 
to FU(H6DO)-29, 
Engine Coolant 
Temperature Sen-
sor.>