COOLING FAN SYSTEM Cooling Fan Circuit

DTC Code DTC Name
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, and sends the signals to the cooling fan ECU to regulate the cooling fans. The cooling fan ECU controls the cooling fan speed based on the duty ratio signal sent from the ECM. By basing its control on the operating conditions, the ECM can control the fan speed optimally using the cooling fan ECU, achieving 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 ignition switch to ON.

    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. Check the operation of the cooling fans while operating them using the GTS.

      OK

      Tester Operation

      Fan Operation

      1-100%

      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 A173 ECM connector.

    2. Turn the ignition switch to ON.

    3. Check the operation of the cooling fans.

      OK

      Cooling fans operate.

    Result

    Proceed to

    OK

    NG
    OK

    REPLACE ECM

    Click hereClick here

    NG

  3. INSPECT COOLING FAN MOTOR (COOLING FAN MOTOR AND NO. 2 COOLING FAN MOTOR)

    1. Inspect the cooling fan motor and No. 2 cooling fan motor.

      Click here

    Result

    Result

    Proceed to

    OK

    A

    NG (Cooling fan motor)

    B

    NG (No. 2 Cooling fan motor)

    C
    B

    REPLACE COOLING FAN MOTOR

    Click here

    C

    REPLACE NO. 2 COOLING FAN MOTOR

    Click here

    A

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

    1. Disconnect the A171 cooling fan ECU connector.

    2. Turn the ignition switch to ON.

    3. A268366C30

      *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

      A171-3 (+B1) - A171-1 (E1)

      Ignition switch ON

      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 A173 ECM connector.

    2. Disconnect the A171 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

      A173-60 (RFC) or A171-2 (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 A171 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

      A171-1 (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 MAIN RELAY

    1. Inspect the FAN MAIN relay.

      Click here

    Result

    Proceed to

    OK

    NG
    NG

    REPLACE FAN MAIN RELAY

    OK

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

    1. Remove the FAN MAIN relay from the engine room relay block and junction block assembly.

    2. Turn the ignition switch to ON.

    3. A350987C02

      *1

      Engine Room Relay Block and Junction Block Assembly

      *2

      FAN MAIN Relay

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

      Standard Voltage

      Tester Connection

      Condition

      Specified Condition

      1 (FAN MAIN relay) - Body ground

      Ignition switch ON

      11 to 14 V

      3 (FAN MAIN relay) - Body ground

      Always

      11 to 14 V

    Result

    Proceed to

    OK

    NG
    NG

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

    OK

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

    1. Disconnect the A171 cooling fan ECU connector.

    2. Remove the FAN MAIN relay from the engine room relay block and 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

      A171-3(+B1) - 5 (FAN MAIN relay)

      Always

      Below 1 Ω

      Standard Resistance (Check for Short)

      Tester Connection

      Condition

      Specified Condition

      A171-3 (+B1) or 5 (FAN MAIN relay) - Body ground

      Always

      10 kΩ or higher

    Result

    Proceed to

    OK

    NG
    OK

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

    NG

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

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

    1. Disconnect the A173 ECM connector.

    2. Disconnect the A171 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

      A173-60 (RFC) - A171-2 (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 - BODY GROUND)

    1. Disconnect the z5 cooling fan motor connector.

    2. A255684C72

      *a

      Component without harness connected

      (Cooling Fan Motor)

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

      Standard Resistance (Check for Short)

      Tester Connection

      Condition

      Specified Condition

      z5-1 (-) - Body ground

      Always

      10 kΩ or higher

    Result

    Proceed to

    OK

    NG
    NG

    REPLACE COOLING FAN MOTOR

    Click here

    OK

  12. CHECK HARNESS AND CONNECTOR (NO. 2 COOLING FAN MOTOR - BODY GROUND)

    1. Disconnect the z9 No. 2 cooling fan motor connector.

    2. A255683C43

      *a

      Component without harness connected

      (No. 2 Cooling Fan Motor)

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

      Standard Resistance (Check for Short)

      Tester Connection

      Condition

      Specified Condition

      z9-1 (-) - Body ground

      Always

      10 kΩ or higher

    Result

    Proceed to

    OK

    NG
    OK

    REPLACE COOLING FAN ECU

    NG

    REPLACE NO. 2 COOLING FAN MOTOR

    Click here