Operating condition

Radiator fan operates depending on the radiator fan speed related to engine coolant temperature or the radiator fan speed related to A/C compressor load, whichever is higher as a load condition.

• Radiator fan speed related to engine coolant temperature

  Courtesy of SUBARU OF AMERICA, INC.

• Radiator fan speed related to A/C compressor load

  Courtesy of SUBARU OF AMERICA, INC.

Diagnosis: 

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

1. CHECK OPERATION OF RADIATOR FAN. 
   1. Turn the ignition switch to OFF.
   2. Connect the delivery mode fuse.

   Does the radiator main fan rotate?

   Yes  : Go to  2.

   No  : Go to  3.

2. CHECK OPERATION OF RADIATOR FAN. 
   1. Turn the ignition switch to OFF.
   2. Connect the delivery mode fuse. Ref. to PRE-DELIVERY INSPECTION>PRE-DELIVERY INSPECTION (PDI) PROCEDURE>FUSE INSTALLATION .

   Does the radiator sub fan rotate?

   Yes  : Radiator main fan system is normal.

   No  : Go to  11.

3. CHECK MAIN FAN RELAY. 
   1. Turn the ignition switch to OFF.
   2. Remove the main fan relay. Ref. to COOLING (H4DOTC)>RADIATOR FAN RELAY>LOCATION .
   3. Measure the resistance between terminals on the main fan relay switch side.

   Is the resistance 1 MΩ or more?

   Yes  : Go to  4.

   No  : Replace the main fan relay, Ref. to COOLING (H4DOTC)>RADIATOR FAN RELAY>LOCATION .

4. CHECK MAIN FAN RELAY. 
   1. Connect the battery to the main fan relay coil side terminal.
   2. Measure the resistance between terminals on the main fan relay switch side.

   Is the resistance less than 1 Ω?

   Yes  : Go to  5.

   NO: Replace the main fan relay. Ref. to COOLING (H4DOTC)>RADIATOR FAN RELAY>LOCATION .

5. CHECK POWER SUPPLY FOR ECM. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from ECM.
   3. Attach the ST between the ECM and engine wiring harness, Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .
   4. Turn the ignition switch to ON.
   5. Measure the voltage between ECM terminal and chassis ground.

      Connector and terminal. 

      (B134) No. 12 (+) - Chassis ground (-):

      (B134) No. 50 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes  : Go to  6.

   No  : Repair the power supply line.

6. CHECK POWER SUPPLY FOR RADIATOR FAN CONTROL MODULE A (MAIN). 
   1. Turn the ignition switch to OFF.
   2. Remove the ST, and connect the connector to ECM.
   3. Disconnect the connector from radiator fan control module (main).
   4. Turn the ignition switch to ON.
   5. Measure the voltage between radiator fan control module (main) terminal and chassis ground.

      Connector and terminal. 

      (F106) No. 1 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes  : Go to  7.

   No  : Repair the power supply line.

7. CHECK HARNESS BETWEEN ECM AND RADIATOR FAN CONTROL A MODULE (MAIN). 
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from ECM.
   3. Measure the resistance between radiator fan control module (main) and ECM connector.

      Connector and terminal. 

      (B134) No. 23 - (F106) No. 2:

   Is the resistance less than 1 Ω?

   Yes  : Go to  8.

   No  : Repair the open circuit of harness between ECM and radiator fan control module (main).

8. CHECK GROUND CIRCUIT FOR RADIATOR FAN CONTROL MODULE (MAIN). 
   1. Connect the connector to ECM and radiator fan control module (main).
   2. Measure the resistance between radiator fan control module (main) connector and chassis ground.

      Connector and terminal. 

      (F106) No. 3 - Chassis ground:

   Is the resistance less than 5 Ω?

   Yes  : Go to  9.

   No  : Repair the open circuit of harness between radiator fan control module (main) connector and chassis ground.

9. CHECK MAIN FAN MOTOR. 
   1. Disconnect the connector from radiator fan control module (main).
   2. Connect the battery positive (+) terminal to terminal No. 1 of the main fan motor, and the ground (-) terminal to terminal No. 2.

   Does the main fan motor rotate?

   Yes  : Go to  10.

   No  : Replace the main fan motor. Ref. to COOLING (H4DOTC)>RADIATOR FAN RELAY>LOCATION .

10. CHECK OUTPUT SIGNAL OF ECM. 
    1. Turn the ignition switch to OFF.
    2. Connect the delivery mode fuse.
    3. Turn the ignition switch to ON.
    4. Check the output waveform using oscilloscope. Ref. to COOLING (H4DOTC)>RADIATOR FAN SYSTEM>RADIATOR FAN CONTROL OUTPUT WAVEFORM .

       Connector and terminal. 

       (B134) No. 23 (+) - Chassis ground (-):

    Is waveform being output?

    Yes  : Replace the radiator fan control module (main). Ref. to COOLING (H4DOTC)>RADIATOR FAN AND FAN MOTOR ASSEMBLY>DISASSEMBLY .

    No  : Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>ENGINE CONTROL MODULE (ECM) .

    NOTE: After replacing the ECM, check again from step  1.
11. CHECK SUB FAN RELAY. 
    1. Turn the ignition switch to OFF.
    2. Remove the sub fan relay.
    3. Measure the resistance between sub fan relay switch terminals.

    Is the resistance 1 MΩ or more?

    Yes  : Go to  12.

    No  : Replace the sub fan relay. Ref. to COOLING (H4DOTC)>RADIATOR FAN RELAY>LOCATION .

12. CHECK SUB FAN RELAY. 
    1. Connect the battery to the terminal on the sub fan relay coil side.
    2. Measure the resistance between sub fan relay switch terminals.

    Is the resistance less than 1 Ω?

    Yes  : Go to  13.

    No  : Replace the sub fan relay. Ref. to COOLING (H4DOTC)>RADIATOR FAN RELAY>LOCATION .

13. CHECK POWER SUPPLY FOR RADIATOR FAN CONTROL MODULE (SUB). 
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from radiator fan control module (sub).
    3. Turn the ignition switch to ON.
    4. Measure the voltage between radiator fan control module (sub) terminal and chassis ground.

       Connector and terminal. 

       (F22) No. 1 (+) - Chassis ground (-):

    Is the voltage 10 V or more?

    Yes  : Go to  14.

    No  : Repair the power supply line.

14. CHECK HARNESS BETWEEN ECM AND RADIATOR FAN CONTROL MODULE (SUB). 
    1. Turn the ignition switch to OFF.
    2. Disconnect the connector from ECM.
    3. Measure the resistance between radiator fan control module (sub) and ECM connector.

       Connector and terminal. 

       (B134) No. 37 - (F22) No. 2:

    Is the resistance less than 1 Ω?

    Yes  : Go to  15.

    No  : Repair the open circuit of harness between ECM and radiator fan control module (sub).

15. CHECK GROUND CIRCUIT FOR RADIATOR FAN CONTROL MODULE (SUB). 
    1. Connect the connector to ECM and radiator fan control module (sub).
    2. Measure the resistance between radiator fan control module (sub) connector and chassis ground.

       Connector and terminal. 

       (F22) No. 3 - Chassis ground:

    Is the resistance less than 5 Ω?

    Yes  : Go to  16.

    No  : Repair the open circuit of harness between radiator fan control module (sub) connector and chassis ground.

16. CHECK SUB FAN MOTOR. 
    1. Disconnect the connector from radiator fan control module (sub).
    2. Connect the battery positive (+) terminal to terminal No. 1 of the sub fan motor, and the ground (-) terminal to terminal No. 2.

    Does the sub fan motor rotate?

    Yes  : Go to  17.

    No  : Replace the sub fan motor, Ref. to COOLING (H4DOTC)>RADIATOR FAN AND FAN MOTOR ASSEMBLY>DISASSEMBLY .

17. CHECK OUTPUT SIGNAL OF ECM. 
    1. Turn the ignition switch to OFF.
    2. Connect the delivery mode fuse.
    3. Turn the ignition switch to ON.
    4. Check the output waveform using oscilloscope, Ref. to COOLING (H4DOTC)>RADIATOR FAN SYSTEM>RADIATOR FAN CONTROL OUTPUT WAVEFORM .

       Connector and terminal. 

       (B134) No. 37 (+) - Chassis ground (-):

    Is waveform being output?

    Yes  : Replace the radiator fan control module (sub). Ref. to COOLING (H4DOTC)>RADIATOR FAN AND FAN MOTOR ASSEMBLY>DISASSEMBLY .

    No  : Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>ENGINE CONTROL MODULE (ECM) .

    NOTE: After replacing the ECM, check again from step  1.