Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 185

CO(w/o STI)-9

Radiator Fan System

COOLING

DIAGNOSIS:

Radiator main fan and radiator sub fans do not rotate under the above operating conditions.

Step

Check

Yes

No

1

CHECK OPERATION OF RADIATOR FAN.
1) Connect the delivery (test) mode connector.
2) Turn the ignition switch to ON.
3) Perform the compulsory operation check for
the radiator fan relay using Subaru Select Mon-
itor.
NOTE:

• When performing a forced operation radiator
fan relay check using the Subaru Select Moni-
tor, the radiator main fan and radiator sub fan
will repeat low speed revolution → high speed
revolution → OFF in this order.
• Subaru Select Monitor
Refer to “Compulsory Valve Operation Check
Mode” for detailed procedures. <Ref. to
EN(H4DOTC)(diag)-64, Compulsory Valve Op-
eration Check Mode.>

Do the radiator main fans and
radiator sub fans rotate at low
speed?

Go to step

2.

Go to step

3.

2

CHECK OPERATION OF RADIATOR FAN.
1) Connect the delivery (test) mode connector.
2) Turn the ignition switch to ON.
3) Perform the compulsory operation check for
the radiator fan relay using Subaru Select Mon-
itor.
NOTE:

• When performing a forced operation radiator
fan relay check using the Subaru Select Moni-
tor, the radiator main fan and radiator sub fan
will repeat low speed revolution → high speed
revolution → OFF in this order.
• Subaru Select Monitor
Refer to “Compulsory Valve Operation Check
Mode” for detailed procedures. <Ref. to
EN(H4DOTC)(diag)-64, Compulsory Valve Op-
eration Check Mode.>

Do the radiator main fans and
radiator sub fans rotate at high
speed?

Radiator main fan
system is normal.

Go to step

27.

3

CHECK POWER SUPPLY TO SUB FAN RE-
LAY.
1) Turn the ignition switch to OFF.
2) Remove the sub fan relay from the relay
holder.
3) Measure the voltage between sub fan relay
connector and chassis ground.

Connector & terminal

(F27) No. 10 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

4.

Go to step

5.

4

CHECK POWER SUPPLY TO SUB FAN RE-
LAY.
1) Turn the ignition switch to ON.
2) Measure the voltage between sub fan relay
connector and chassis ground.

Connector & terminal

(F27) No. 13 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

7.

Go to step

6.

5

CHECK FUSE.
1) Turn the ignition switch to OFF.
2) Remove the fuse No. 3.
3) Check the condition of fuse.

Is the fuse blown out?

Replace the fuse. Repair the power

supply line.

CO(w/o STI)-10

Radiator Fan System

COOLING

6

CHECK FUSE.
1) Turn the ignition switch to OFF.
2) Remove the fuse No. 22.
3) Check the condition of fuse.

Is the fuse blown out?

Replace the fuse. Repair the power

supply line.

7

CHECK SUB FAN RELAY.
1) Turn the ignition switch to OFF.
2) Measure the resistance between sub fan
relay terminals.

Terminals

No. 10 — No. 11:

Is the resistance 1 MΩ or
more?

Go to step

8.

Replace the sub
fan relay.

8

CHECK SUB FAN RELAY.
1) Connect the battery to terminals No. 12 and
No. 13 of the sub fan relay.
2) Measure the resistance between sub fan
relay terminals.

Terminals

No. 10 — No. 11:

Is the resistance less than 1 Ω? Go to step

9.

Replace the sub
fan relay.

9

CHECK HARNESS BETWEEN SUB FAN RE-
LAY CONNECTOR AND SUB FAN MOTOR
CONNECTOR.
1) Disconnect the connector from the sub fan
motor.
2) Measure the resistance of harness between
sub fan relay connector and sub fan motor con-
nector.

Connector & terminal

(F16) No. 1 — (F27) No. 11:

Is the resistance less than 1 Ω? Go to step

10.

Repair the open
circuit of harness
between sub fan
relay connector
and sub fan motor
connector.

10

CHECK HARNESS BETWEEN SUB FAN MO-
TOR CONNECTOR AND MAIN FAN RELAY 2
CONNECTOR.
1) Remove main fan relay 2 from the relay
holder.
2) Measure the resistance of harness between
sub fan motor connector and main fan relay 2
connector.

Connector & terminal

(F16) No. 2 — (F27) No. 18:

Is the resistance less than 1 Ω? Go to step

11.

Repair the open
circuit of the har-
ness between sub
fan motor connec-
tor and main fan
relay 2 connector.

11

CHECK FOR POOR CONTACT.
Check poor contact of sub fan motor connector.

Is there poor contact of the sub
fan motor connector?

Repair the poor
contact of sub fan
motor connector.

Go to step

12.

12

CHECK SUB FAN MOTOR.
Connect the battery positive (+) terminal to ter-
minal No. 1 of the sub fan motor, and the ground
(–) terminal to terminal No. 2.

Does the radiator sub fan
rotate?

Go to step

13.

Replace the sub
fan motor.

13

CHECK MAIN FAN RELAY 2.
Measure the resistance between main fan relay
2 terminals.

Terminals

No. 21 — No. 18:

Is the resistance less than 1 Ω? Go to step

14.

Replace the main
fan relay 2.

14

CHECK HARNESS BETWEEN MAIN FAN
RELAY 2 CONNECTOR AND MAIN FAN MO-
TOR CONNECTOR.
1) Disconnect the connector from the main fan
motor.
2) Measure the resistance of the harness
between main fan relay 2 connector and main
fan motor connector.

Connector & terminal

(F17) No. 1 — (F27) No. 21:

Is the resistance less than 1 Ω? Go to step

15.

Repair the open
circuit of the har-
ness between
main fan relay 2
connector and
main fan motor
connector.

Step

Check

Yes

No

CO(w/o STI)-11

Radiator Fan System

COOLING

15

CHECK MAIN FAN MOTOR AND GROUND
CIRCUIT.
Measure the resistance between main fan
motor connector and chassis ground.

Connector & terminal

(F17) No. 2 — Chassis ground:

Is the resistance less than 5 Ω? Go to step

16.

Repair the open
circuit of the har-
ness between
main fan motor
connector and
chassis ground.

16

CHECK FOR POOR CONTACT.
Check poor contact of main fan motor connec-
tor.

Is there poor contact of the
main fan motor connector?

Repair the poor
contact of main fan
motor connector.

Go to step

17.

17

CHECK MAIN FAN MOTOR.
Connect the battery positive (+) terminal to ter-
minal No. 1 of the main fan motor, and the
ground (–) terminal to terminal No. 2.

Does the radiator main fan
rotate?

Go to step

18.

Replace the main
fan motor.

18

CHECK HARNESS BETWEEN SUB FAN RE-
LAY CONNECTOR AND ECM.
1) Disconnect the connector from ECM.
2) Measure the resistance between the sub
fan relay connector and ECM connector.

Connector & terminal

(B135) No. 11 — (F27) No. 12:

Is the resistance less than 1 Ω? Go to step

19.

Repair the open
circuit of harness
between sub fan
relay connector
and ECM.

19

CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.

Is there poor contact of ECM
connector?

Repair the poor
contact of ECM
connector.

Check the DTC.
Repair the trouble
cause. <Ref. to
EN(H4DOTC)(diag)
-48, Read Diagnos-
tic Trouble Code
(DTC).>

20

CHECK MAIN FAN RELAY 1.
1) Turn the ignition switch to OFF.
2) Remove main fan relay 1 from the main fuse
box.
3) Measure the resistance between terminals
of main fan relay 1 switch.

Is the resistance 1 MΩ or
more?

Go to step

21.

Replace the main
fan relay 1.

21

CHECK MAIN FAN RELAY 1.
1) Connect the main fan relay 1 coil side termi-
nal to the battery.
2) Measure the resistance between terminals
of main fan relay 1 switch.

Is the resistance less than 1 Ω? Go to step

22.

Replace the main
fan relay 1.

22

CHECK HARNESS BETWEEN MAIN FAN
RELAY 1 CONNECTOR AND MAIN FAN MO-
TOR CONNECTOR.
1) Disconnect the connector from the main fan
motor.
2) Measure the resistance of the harness
between main fan relay 1 connector and main
fan motor connector.

Connector & terminal

(F17) No. 1 — (F36) No. 6:

Is the resistance less than 1 Ω? Go to step

23.

Repair the open
circuit of the har-
ness between
main fan relay 1
connector and
main fan motor
connector.

23

CHECK HARNESS BETWEEN MAIN FAN
RELAY 1 CONNECTOR AND ECM.
1) Disconnect the connector from ECM.
2) Measure the resistance between the main
fan relay 1 connector and ECM connector.

Connector & terminal

(B135) No. 12 — (B143) No. 7:

Is the resistance less than 1 Ω? Go to step

24.

Repair the open
circuit of the har-
ness between
main fan relay 1
connector and
ECM.

Step

Check

Yes

No

CO(w/o STI)-12

Radiator Fan System

COOLING

24

CHECK HARNESS BETWEEN MAIN FAN
RELAY 2 CONNECTOR AND ECM.
Measure the resistance between the main fan
relay 2 connector and ECM connector.

Connector & terminal

(B135) No. 12 — (F27) No. 22:

Is the resistance less than 1 Ω? Go to step

25.

Repair the open
circuit of the har-
ness between
main fan relay 2
connector and
ECM.

25

CHECK FUSE.
1) Turn the ignition switch to OFF.
2) Remove the fuse No. 2 and No. 26.
3) Check the condition of fuse.

Is the fuse blown out?

Replace the fuse. Go to step

26.

26

CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.

Is there poor contact of ECM
connector?

Repair the poor
contact of ECM
connector.

Repair the power
supply circuit to the
main fuse box.

27

CHECK OPERATION OF RADIATOR FAN.
If the both fans do not rotate at high speed in the
condition of step 2, check whether the radiator
sub fan is rotating.

Does the radiator sub fan
rotate?

Go to step

20.

Go to step

28.

28

CHECK GROUND CIRCUIT OF MAIN FAN
RELAY 2.
1) Remove main fan relay 2 from the relay
holder.
2) Measure the resistance between main fan
relay 2 connector and chassis ground.

Connector & terminal

(F27) No. 19 — Chassis ground:

Is the resistance less than 1 Ω? Go to step

29.

Repair the open
circuit of harness
between main fan
relay 2 connector
and chassis
ground.

29

CHECK POWER SUPPLY TO MAIN FAN RE-
LAY 2.
1) Turn the ignition switch to ON.
2) Measure the voltage between main fan relay
2 connector and chassis ground.

Connector & terminal

(F27) No. 20 (+) — Chassis ground (–):

Is the voltage 10 V or more?

Go to step

30.

Repair the power
supply line.

30

CHECK MAIN FAN RELAY 2.
1) Turn the ignition switch to OFF.
2) Remove the main fan relay 2.
3) Measure the resistance between main fan
relay 2 terminals.

Terminals

No. 18 — No. 19:

Is the resistance 1 MΩ or
more?

Go to step

31.

Replace the main
fan relay 2.

31

CHECK MAIN FAN RELAY 2.
1) Connect the battery to terminals No. 20 and
No. 22 of the main fan relay 2.
2) Measure the resistance between main fan
relay 2 terminals.

Terminals

No. 18 — No. 19:

Is the resistance less than 1 Ω? Go to step

23.

Replace the main
fan relay 2.

Step

Check

Yes

No