COOLING FAN SYSTEM Cooling Fan Circuit

DESCRIPTION

The ECM calculates an appropriate cooling fan speed based on the engine coolant temperature, air conditioning switch condition, refrigerant pressure, engine speed and vehicle speed. The cooling fan ECUs control each cooling fan speed based on the duty cycle calculated by the ECM. By optimally controlling the cooling fan speed via the cooling fan ECUs based on the conditions of the vehicle, the ECM can achieve both high cooling performance and quietness.

WIRING DIAGRAM

Refer to the System Diagram.

Click here

CAUTION / NOTICE / HINT

Note


  • Inspect the fuses for circuits related to this system before performing the following procedure.

  • Before replacing the ECM, refer to Service Bulletin.

PROCEDURE


  1. PERFORM ACTIVE TEST USING GTS (CONTROL THE ENGINE COOLING FAN DUTY RATIO)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine / Active Test / Control the Engine Cooling Fan Duty Ratio.


      Powertrain > Engine > Active Test
      Tester Display
      Control the Engine Cooling Fan Duty Ratio

    5. Perform the Active Test according to the display on the GTS.

      OK
      Active Test Operation Fan Operation
      30 - 100% Cooling fans operate
      0% Cooling fans stop
      Result
      Result Proceed to
      OK A
      NG (Cooling fans do not operate) B
      NG (Cooling fans do not stop) C

    A

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE Click here

    C

    CHECK HARNESS AND CONNECTOR (ECM - COOLING FAN ECU) Click here

    B

  2. CHECK COOLING FAN SYSTEM


    1. Disconnect the D2 ECM connector.

    2. Turn the engine switch on (IG).

    3. Check the operation of the cooling fans.

      OK
      Cooling fans operate.
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE ECM Click here

    NG

  3. INSPECT COOLING FAN MOTOR (COOLING FAN MOTOR LH AND COOLING FAN MOTOR RH)


    1. Inspect the cooling fan motor LH and cooling fan motor RH.

      Click here

      Result
      Result Proceed to
      OK A
      NG (Cooling fan motor LH) B
      NG (Cooling fan motor RH) C

    B

    REPLACE COOLING FAN MOTOR LH Click here

    C

    REPLACE COOLING FAN MOTOR RH Click here

    A

  4. CHECK HARNESS AND CONNECTOR (COOLING FAN ECU POWER SOURCE CIRCUIT)


    1. Disconnect the A4 cooling fan ECU connector.

    2. Turn the engine switch on (IG).

    3. A01VV0IC34
      *a

      Front view of wire harness connector

      (to Cooling Fan ECU)

      Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      A4-3 (+B1) - A4-1 (E1) Engine switch on (IG) 11 to 14 V
      Result
      Proceed to
      OK
      NG

    NG

    CHECK HARNESS AND CONNECTOR (COOLING FAN ECU - BODY GROUND) Click here

    OK

  5. CHECK HARNESS AND CONNECTOR (ECM - COOLING FAN ECU)


    1. Disconnect the D2 ECM connector.

    2. Disconnect the A4 cooling fan ECU connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      D2-136 (RFC) or A4-2 (SI) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE COOLING FAN ECU

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - COOLING FAN ECU)

  6. CHECK HARNESS AND CONNECTOR (COOLING FAN ECU - BODY GROUND)


    1. Disconnect the A4 cooling fan ECU connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      A4-1 (E1) - Body ground Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (COOLING FAN ECU - BODY GROUND)

    OK

  7. INSPECT FAN RELAY


    1. Inspect the FAN relay.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE FAN RELAY

    OK

  8. CHECK HARNESS AND CONNECTOR (FAN RELAY POWER SOURCE CIRCUIT)


    1. Remove the FAN relay from the No. 1 engine room relay block and No. 1 junction block assembly.

    2. Turn the engine switch on (IG).

    3. B007YELC03
      *1 No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
      *2 FAN Relay

      Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      1 (FAN relay) - Body ground Engine switch on (IG) 11 to 14 V
      3 (FAN relay) - Body ground Always 11 to 14 V
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (FAN RELAY POWER SOURCE CIRCUIT)

    OK

  9. CHECK HARNESS AND CONNECTOR (COOLING FAN ECU - FAN RELAY)


    1. Disconnect the A4 cooling fan ECU connector.

    2. Remove the FAN relay from the No. 1 engine room relay block and No. 1 junction block assembly.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      A4-3(+B1) - 5 (FAN relay) Always Below 1 Ω
      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      A4-3 (+B1) or 5 (FAN relay) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    OK

    REPAIR OR REPLACE HARNESS OR CONNECTOR (FAN RELAY - BODY GROUND)

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (COOLING FAN ECU - FAN RELAY)

  10. CHECK HARNESS AND CONNECTOR (ECM - COOLING FAN ECU)


    1. Disconnect the D2 ECM connector.

    2. Disconnect the A4 cooling fan ECU connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Open)
      Tester Connection Condition Specified Condition
      D2-136 (RFC) - A4-2 (SI) Always Below 1 Ω
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - COOLING FAN ECU)

    OK

  11. CHECK HARNESS AND CONNECTOR (COOLING FAN MOTOR LH - BODY GROUND)


    1. Disconnect the z2 cooling fan motor LH connector.

    2. A01VWTMC51
      *a

      Component without harness connected

      (Cooling Fan Motor LH)

      Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      z2-1 (-) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPLACE COOLING FAN MOTOR LH Click here

    OK

  12. CHECK HARNESS AND CONNECTOR (COOLING FAN MOTOR RH - BODY GROUND)


    1. Disconnect the z1 cooling fan motor RH connector.

    2. A01VVC1C06
      *a

      Component without harness connected

      (Cooling Fan Motor RH)

      Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for Short)
      Tester Connection Condition Specified Condition
      z1-1 (-) - Body ground Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    OK

    REPLACE COOLING FAN ECU

    NG

    REPLACE COOLING FAN MOTOR RH Click here