Subaru Legacy III (2000-2003 year). Manual — part 128

EN(H4SO)-124

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

M: DTC P0118 — ENGINE COOLANT TEMPERATURE CIRCUIT HIGH INPUT —

• DTC DETECTING CONDITION:

• Immediately at fault recognition

• TROUBLE SYMPTOM:

• Hard to start
• Erroneous idling
• Poor driving performance

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-01125

19

12

9

13

B135 ECM

2

1

E2

B21

E8

ENGINE

COOLANT

TEMPERATURE

SENSOR

E8

B21

1 2

3 4

5

6 7

8

9 10

11 12

13

14 15

16

17 18

19 20

1 2

3

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

B135

B83

1 2 3 4 5 6

B83

3

1

FG

2

4

EG

: FOR G.C.C COUNTRIES MODEL

: EXCEPT FOR G.C.C COUNTRIES MODEL

FG

EG

EN(H4SO)-125

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

Step

Value

Yes

No

1

CHECK CURRENT DATA.
1) Start engine.
2) Read data of engine coolant temperature

sensor signal using Subaru Select Monitor
or OBD-II general scan tool.
Is the measured value less than the speci-
fied value?

NOTE:

•Subaru Select Monitor
For detailed operation procedure, refer to the
“READ CURRENT DATA FOR ENGINE”.
<Ref. to EN(H4SO)-32, Subaru Select Moni-
tor.>
•OBD-II general scan tool
For detailed operation procedures, refer to the
OBD-II General Scan Tool Instruction Manual.

−

40

°

C (

−

40

°

F)

Go to step 2.

Repair poor con-
tact.

NOTE:
In this case, repair
the following:
• Poor contact in
engine coolant
temperature sen-
sor
• Poor contact in
ECM
• Poor contact in
coupling connector
• Poor contact in
joint connector

2

CHECK HARNESS BETWEEN ENGINE
COOLANT TEMPERATURE SENSOR AND
ECM CONNECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from engine coolant

temperature sensor.

3) Measure voltage between engine coolant

temperature sensor connector and engine
ground.

Connector & terminal

(E8) No. 1 (+) — Engine ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Repair battery
short circuit in har-
ness between
ECM and engine
coolant tempera-
ture sensor con-
nector.

Go to step 3.

3

CHECK HARNESS BETWEEN ENGINE
COOLANT TEMPERATURE SENSOR AND
ECM CONNECTOR.
1) Turn ignition switch to ON.
2) Measure voltage between engine coolant

temperature sensor connector and engine
ground.

Connector & terminal

(E8) No. 1 (+) — Engine ground (

−−−−

):

Does the measured value exceed the spec-
ified value?

10 V

Repair battery
short circuit in har-
ness between
ECM and engine
coolant tempera-
ture sensor con-
nector.

Go to step 4.

EN(H4SO)-126

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(H4SO)-26,
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(H4SO)-127

ENGINE (DIAGNOSTICS)

DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)

MEMO: