Subaru Legacy IV (2008 year). Manual - part 325

EN(H4DOTC)(diag)-121

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

S: DTC P0117 ENGINE COOLANT TEMPERATURE CIRCUIT LOW

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-36, DTC P0117 ENGINE COOLANT TEMPERATURE
CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Hard to start
• Improper idling
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
52, OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-43, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-05672

B134

34

E8

2

1

12

6

E8

B134

B21

E2

B21

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

1 2

29

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

33 34

29

32

30 31

ENGINE

COOLANT

TEMPERATURE 

SENSOR

ECM

EN(H4DOTC)(diag)-122

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of engine coolant tempera-
ture sensor signal using Subaru Select Monitor 
or general scan tool.

NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-34, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.

Is the engine coolant tempera-
ture 150°C (302°F) or higher?

Go to step 2.

Even if DTC is 
detected, the cir-
cuit has returned to 
a normal condition 
at this time. Repro-
duce the failure, 
and then perform 
the diagnosis 
again.

NOTE:
In this case, tem-
porary poor con-
tact of connector
may be the cause.

2

CHECK HARNESS BETWEEN ECM AND EN-
GINE COOLANT TEMPERATURE SENSOR 
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and 
engine coolant temperature sensor.
3) Measure the resistance between ECM and 
chassis ground.

Connector & terminal

(B134) No. 34 — Chassis ground:

Is the resistance 1 M

: or 

more?

Replace the 
engine coolant 
temperature sen-
sor. <Ref. to 
FU(H4DOTC)-31, 
Engine Coolant 
Temperature Sen-
sor.>

Repair the short 
circuit to ground in 
harness between 
ECM and engine 
coolant tempera-
ture sensor.

EN(H4DOTC)(diag)-123

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

T: DTC P0118 ENGINE COOLANT TEMPERATURE CIRCUIT HIGH

DTC DETECTING CONDITION:
• Immediately at fault recognition
• GENERAL DESCRIPTION <Ref. to GD(H4DOTC)-37, DTC P0118 ENGINE COOLANT TEMPERATURE
CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
• Hard to start
• Improper idling
• Poor driving performance

CAUTION:
After repair or replacement of faulty parts, perform Clear Memory Mode <Ref. to EN(H4DOTC)(diag)-
52, OPERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(H4DOTC)(diag)-43, PRO-
CEDURE, Inspection Mode.>.
WIRING DIAGRAM:

EN-05672

B134

34

E8

2

1

12

6

E8

B134

B21

E2

B21

1 2 3 4

12 13 14 15

5 6 7 8

16 17 18 19

9 10 11

20 21 22

23 24 25 26 27 28 29 30 31 32 33

35

34

37

36

39

38

41

40

43

42

44

45

47

46

49

48

51

50

53

52

54

1 2

29

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

33 34

29

32

30 31

ENGINE

COOLANT

TEMPERATURE 

SENSOR

ECM

EN(H4DOTC)(diag)-124

Diagnostic Procedure with Diagnostic Trouble Code (DTC)

ENGINE (DIAGNOSTICS)

Step

Check

Yes

No

1

CHECK CURRENT DATA.
1) Start the engine.
2) Read the data of engine coolant tempera-
ture sensor signal using Subaru Select Monitor 
or general scan tool.

NOTE:
• Subaru Select Monitor
For detailed operation procedure, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(H4DOTC)(diag)-34, Subaru Select Moni-
tor.>
• General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.

Is the engine coolant tempera-
ture less than –40°C (–40°F) ?

Go to step 2.

Even if DTC is 
detected, the cir-
cuit has returned to 
a normal condition 
at this time. Repro-
duce the failure, 
and then perform 
the diagnosis 
again.

NOTE:
In this case, tem-
porary poor con-
tact of connector
may be the cause.

2

CHECK POOR CONTACT.
Check for poor contact in ECM and engine cool-
ant temperature sensor connector.

Is there poor contact in ECM or 
engine coolant temperature 
sensor connector?

Repair the poor 
contact in ECM or 
engine coolant 
temperature sen-
sor connector.

Go to step 3.

3

CHECK HARNESS BETWEEN ECM AND EN-
GINE COOLANT TEMPERATURE SENSOR 
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and 
engine coolant temperature sensor.
3) Measure the resistance of harness between 
ECM and engine coolant temperature sensor 
connector.

Connector & terminal

(B134) No. 34 — (E8) No. 2:
(B134) No. 29 — (E8) No. 1:

Is the resistance less than 1 

:? Go to step 4.

Repair the harness 
and connector.

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

4

CHECK HARNESS BETWEEN ECM AND EN-
GINE COOLANT TEMPERATURE SENSOR 
CONNECTOR.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM and 
chassis ground.

Connector & terminal

(B134) No. 34 (+) — Chassis ground (–):

Is the voltage 5 V or more?

Repair the short 
circuit to power in 
harness between 
ECM and engine 
coolant tempera-
ture sensor con-
nector.

Replace the 
engine coolant 
temperature sen-
sor. <Ref. to 
FU(H4DOTC)-31, 
Engine Coolant 
Temperature Sen-
sor.>