COOLING FAN ECU ON-VEHICLE INSPECTION


  1. CHECK COOLING FAN ECU


    1. Remove the front controller cover.

    2. A01GN2V

      Using 2 screwdrivers, detach the 2 claws and disconnect the front controller.

      Tech Tips

      Tape the screwdriver tips before use.

    3. Check the resistance of the wire harness between the front controller B14-22 (FAN1) and cooling fan ECU A9-2 (SI).

      A01GJJDE03
      Standard resistance
      Tester Connection Specified Condition
      B14-22 (FAN1) - A9-2 (SI) Below 1 Ω

      B14-22 (FAN1) - Body ground

      A9-2 (SI) - Body ground

      		 10 kΩ or higher

      If the result is not as specified, repair or replace the wire harness or connector.

    4. Check the output signal from the front controller.

      Tech Tips

      Be sure to perform the inspection when the engine coolant temperature is less than 92°C (198°F).


      1. Set the oscilloscope probe to the terminal B14-22 (FAN1) of the front controller.

        A01GJHGE04

      2. Connect the intelligent tester to the DLC3.

      3. Using the intelligent tester, check the waveform.

        Tech Tips

        Select the following menu items: Power train / Engine / Active Test / Cooling Fan.

        A01GN1QE01
        Standard waveform
        Condition Input Signal

        Engine stopped

        (Engine switch on (IG))

        Waveform 1

        (Duty ratio 0%)

        Engine idling

        (A/C OFF)

        Waveform 1

        (Duty ratio 0%)

        Engine idling

        (A/C ON)

        Waveform 2

        (Duty ratio 50 to 70%)

        Engine idling

        (Engine coolant temperature sensor connector disconnected)

        Waveform 3

        (Duty ratio 60 to 70%)

        If the output signal is abnormal, there is a malfunction in the ECM or front controller.

    5. A01GKYAE04

      Check the input voltage.


      1. Disconnect the cooling fan ECU connector.

      2. Turn the engine switch on (IG). Check the voltage of the A9-3 (+B1) terminal on the wire harness side.

        Standard voltage
        11 to 14 V

        If the result is not as specified, check the power source system (H-fuse, fuse, wire harness and relay).

      3. Connect the cooling fan ECU connector.

    6. Check wire harness (cooling fan ECU and body ground).


      1. Disconnect the cooling fan ECU connector.

      2. Measure the resistance of the A9-1 (E1) and body ground.

        Standard resistance
        Below 1 Ω

        If the result is not as specified, check the wire harness or connector.

      3. Connect the cooling fan ECU connector.

    7. Check the cooling fan motor Click here.

      If the result is not as specified, replace the cooling fan motor.

    8. A01GKUWE01

      Check the cooling fan motor operation.


      1. Disconnect the cooling fan ECU connector.

      2. Connect the battery to the cooling fan ECU at terminals 3 (+B1) and 1 (E1).

      3. Check that the cooling fan motor rotates.

        If it does not operate, replace the cooling fan ECU.