Subaru Legacy III (2000-2003 year). Manual - part 336

EN(H6DO)-146

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

4

CHECK HARNESS BETWEEN ENGINE 
COOLANT TEMPERATURE SENSOR AND 
ECM CONNECTOR.
Measure voltage between engine coolant tem-
perature sensor connector and engine ground.

Connector & terminal

(E8) No. 1 (+) — Engine ground (

−−−−

):

Does the measured value exceed the specified 
value?

4 V

Go to step 5.

Repair harness 
and connector.

NOTE:
In this case, repair
the following:
• Open circuit in 
harness between 
ECM and engine 
coolant tempera-
ture sensor con-
nector
• Poor contact in 
engine coolant 
temperature sen-
sor connector
• Poor contact in 
ECM connector
• Poor contact in 
coupling connector
• Poor contact in 
joint connector

5

CHECK HARNESS BETWEEN ENGINE 
COOLANT TEMPERATURE SENSOR AND 
ECM CONNECTOR.
1) Turn ignition switch to OFF.
2) Measure resistance of harness between 

engine coolant temperature sensor connec-
tor and engine ground.

Connector & terminal

(E8) No. 2 — Engine ground:

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

5 

Ω

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

Repair harness 
and connector.

NOTE:
In this case, repair
the following:

• Open circuit in 
harness between 
ECM and engine 
coolant tempera-
ture sensor con-
nector
• Poor contact in 
engine coolant 
temperature sen-
sor connector
• Poor contact in 
ECM connector
• Poor contact in 
coupling connector
• Poor contact in 
joint connector

Step

Value

Yes

No

EN(H6DO)-147

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO:

EN(H6DO)-148

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Q: DTC P0121 — THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT 

RANGE/PERFORMANCE —

• DTC DETECTING CONDITION:

• Two consecutive driving cycles with fault

• 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)-149

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
P0121.

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