Mitsubishi Lancer Evolution IX. Manual - part 656

TROUBLESHOOTING

ENGINE COOLING

14-9

STEP 11. Check the harness wire between 
engine-ECU connector C-121 and fan controller 
connector A-17.
NOTE: 

AC210877AC

Connector: A-13 <LHD>

A-13 (B)

AC310903AB

Connector: C-31 <RHD>

C-31

If intermediate connector A-13 <LHD> terminal 2 and 
intermediate connector C-31 <RHD> terminal 14 is 
damaged, repair or replace it. Refer to GROUP 00, 
How to Use Troubleshooting/Inspection Service 
Points 

P.00-5

.

AC505254 AC

Connector: C-121 <LHD>

C-121 (GR)

Engine-ECU

15
29

2221

23
3534

7

8

16

18

19

17

20

31

32

33

30

5

6

11 10

12

13

14

26

2827

25

3

4

2

9

24

1

JAE

Component side

AC505255 AC

Connector: C-121 <RHD>

C-121 (GR)

Engine-ECU

15
29

2221

23
3534

7

8

16

18

19

17

20

31

32

33

30

5

6

11 10

12

13

14

26

2827

25

3

4

2

9

24

1

JAE

Component side

AC210859

Connector: A-17

A-17 (GR)

AD

Fan controller

Component side

Q: Are the harness wires between engine-ECU 

connector C-121 terminal 18 and fan controller 
connector A-17 terminal 2 damaged?
YES : 

Repair or replace them, then go to Step 13.

NO : 

Go to Step 12.

TROUBLESHOOTING

ENGINE COOLING

14-10

STEP 12. Check the fan controller at engine-ECU 
connector C-121.

AC505254

16

25

10

24

1
9

2

4

27

13

26

11

3

12

2829

1415

3031

1718

33

32

6

20

5

19

21

35

34

8

23

7

22

JAE

AB

Connector: C-121 <LHD>

Harness side

C-121 (GR)

Engine-ECU

AC505255

16

25

10

24

1
9

2

4

27

13

26

11

3

12

2829

1415

3031

1718

33

32

6

20

5

19

21

35

34

8

23

7

22

JAE

AB

Connector: C-121 <RHD>

Harness side

C-121 (GR)

Engine-ECU

(1) Do not disconnect engine-ECU connector C-121.

(2) Pull out terminal No.18.
(3) Turn the ignition switch to the "ON" position.

Q: Does the cooling fan motor operate?

YES : 

Replace the engine-ECU. Then go to Step 

13.

NO : 

Replace the fan controller. Then go to Step 
13.

STEP 13. Check the symptoms.

Q: Does the cooling fan operate correctly?

YES : 

The procedure is complete.

NO : 

Return to Step 1.

INSPECTION PROCEDURE 2: Cooling fan does not change speed or does not stop

NOTE: If the engine coolant temperature reaches 110

°

C or higher, the cooling fan control runs the cooling fan 

for up to 5 minutes even after the ignition switch is turned to the "LOCK" (OFF) position (the fan stops its rota-
tion when the engine coolant temperature decreases to 110

°

C or lower).

COOLING FAN DRIVE CIRCUIT

 Refer to 

P.14-4

.

CIRCUIT OPERATION

• The fan controller is powered from fusible link 

No.2.

• The engine-ECU judges the required revolution 

speed of cooling fan motor using the input signals 
transmitted from A/C switch, vehicle speed sen-
sor and engine coolant temperature sensor. The 
engine-ECU activates the fan controller to drive 
the cooling fan motor.

TROUBLESHOOTING

ENGINE COOLING

14-11

TECHNICAL DESCRIPTION

• The fan controller has variable control of the cool-

ing fan motor speed using signals transmitted 
from the engine-ECU.

TROUBLESHOOTING HINTS

• Malfunction of fan control relay

• Malfunction of fan controller

• Malfunction of engine-ECU

DIAGNOSIS

STEP 1. Check the fan control relay.
 Refer to 

P.14-17

.

Q: Is the fan control relay in good condition?

YES : 

Go to Step 2.

NO : 

Replace the part, then go to Step 8.

STEP 2. Check the harness wire between fan 
control relay connector A-09X terminal 2 and fan 
controller connector A-17 terminal 3.

AC310900AB

Connector: A-09X

A-09X

3

1

4

2

Relay box 
side

AC210859

Connector: A-17

A-17 (GR)

AD

Fan controller

Component side

Q: Are the harness wire between fan control relay 

connector A-09X and fan controller connector A-17 
damaged?
YES : 

Repair or replace the part, then go to Step 

6.

NO : 

Go to Step 3.

STEP 3. Measure the output circuit voltage at 
engine-ECU connector C-121 terminal 18 by 
backprobing.

AC505254

16

25

10

24

1
9

2

4

27

13

26

11

3

12

2829

1415

3031

1718

33

32

6

20

5

19

21

35

34

8

23

7

22

JAE

AB

Connector: C-121 <LHD>

Harness side

C-121 (GR)

Engine-ECU

AC505255

16

25

10

24

1
9

2

4

27

13

26

11

3

12

2829

1415

3031

1718

33

32

6

20

5

19

21

35

34

8

23

7

22

JAE

AB

Connector: C-121 <RHD>

Harness side

C-121 (GR)

Engine-ECU

(1) Do not disconnect engine-ECU connector C-121.
(2) Start the engine and allow it to idle.
(3) Measure the voltage between terminal No.18 and 

earth by backprobing.

• The voltage should measure less than 0.3 volt 

when the cooling fan is not operating.

Q: Is the voltage less than 0.3 volt when the cooling 

fan is not operating?
YES : 

Go to Step 6.

NO : 

Go to Step 4.

TROUBLESHOOTING

ENGINE COOLING

14-12

STEP 4. Measure the output circuit voltage at 
engine-ECU connector C-121 terminal 18 by 
backprobing.

AC505254

16

25

10

24

1
9

2

4

27

13

26

11

3

12

2829

1415

3031

1718

33

32

6

20

5

19

21

35

34

8

23

7

22

JAE

AB

Connector: C-121 <LHD>

Harness side

C-121 (GR)

Engine-ECU

AC505255

16

25

10

24

1
9

2

4

27

13

26

11

3

12

2829

1415

3031

1718

33

32

6

20

5

19

21

35

34

8

23

7

22

JAE

AB

Connector: C-121 <RHD>

Harness side

C-121 (GR)

Engine-ECU

(1) Do not disconnect engine-ECU connector C-121.

(2) Start the engine and allow it to idle.
(3) Turn the A/C switch to the "ON" position.
(4) Measure the voltage between terminal No.18 and 

earth by backprobing.

• The voltage should measure 0.7 volt or more 

when the cooling fan is operating.

Q: Is the voltage 0.7 volt or more when the cooling fan 

is operating?
YES : 

Go to Step 6.

NO : 

Go to Step 5.