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Cooling Fan Circuit [12/2023 - ]: Procedure

WARNING: This page is about a different car, the 2024 Lexus TX 550h+. However, it is still accessible from the selected car via links, so may be relevant.
  1. PERFORM ACTIVE TEST USING GTS (CONTROL THE ENGINE COOLING FAN DUTY RATIO) 
    1. Check the operation of the cooling fan while operating it using the GTS.

      Powertrain > Engine > Active Test 

      Tester Display
      Control the Engine Cooling Fan Duty Ratio

      OK

      GTS Operation Fan Operation
      30 - 100% Cooling fan operates
      0% Cooling fan stops

      Result

      Result Proceed to
      OK A
      Cooling fan does not operate B
      Cooling fan does not stop C

    Result: 

    A 

    PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to  PROBLEM SYMPTOMS TABLE [12/2023 - ]  

    Result: 

    C 

    See step  9

    Result: 

    B 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (FAN WITH MOTOR ASSEMBLY - BODY GROUND) 
    1. Disconnect the A18 fan with motor assembly connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A18-1 (E1) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (FAN WITH MOTOR ASSEMBLY POWER SOURCE) 
    1. Disconnect the A18 fan with motor assembly connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A18-2 (+B1) - A18-1 (E1) Always 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR (FAN WITH MOTOR ASSEMBLY - AUXILIARY BATTERY) 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (FAN WITH MOTOR ASSEMBLY POWER SOURCE) 
    1. Disconnect the A19 fan with motor assembly connector.
    2. Turn the ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A19-1 (IGS1) - Body ground Ignition switch ON 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    See step  7

    Result: 

    OK 

    See step  5

  5. CHECK HARNESS AND CONNECTOR (FAN WITH MOTOR ASSEMBLY - ECM - HYBRID VEHICLE CONTROL ECU) 
    1. Disconnect the A19 fan with motor assembly connector.
    2. Disconnect the B86 ECM connector.
    3. Disconnect the B88 hybrid vehicle control ECU connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A19-2 (SI) - B86-60 (RFC) Always Below 1 Ω
      A19-2 (SI) - B88-46 (RFC) Always Below 1 Ω
      A19-2 (SI) or B86-60 (RFC) - Body ground Always 10 kΩ or higher
      A19-2 (SI) or B88-46 (RFC) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  6

  6. INSPECT ECM (RFC TERMINAL) 
    1. Disconnect the A17 fan with motor assembly connector.
    2. Disconnect the A18 hybrid vehicle control ECU connector.
    3. Operate the cooling fan motor (fan with motor assembly) using the Active Test function and measure the resistance according to the value(s) in the table below.

      Powertrain > Engine > Active Test 

      Tester Display
      Control the Engine Cooling Fan Duty Ratio

      Standard Resistance

      Tester Connection GTS Operation Specified Condition
      A19-2 (SI) - Body ground Before Active Test (0%) → During Active Test (100%) Before Active Test (0%): Resistance is stable → During Active Test (100%): Resistance fluctuates*

      HINT: 

      *: Using the Active Test, duty control of the transistors in the ECM will be performed. Due to the duty control, resistance of the RFC terminal will be unstable during the Active Test. If the resistance is stable before the Active Test and fluctuates while performing the Active Test, it can be determined that the transistor is operating. If the transistor does not operate during the Active Test, the ECM may be malfunctioning.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE FAN WITH MOTOR ASSEMBLY. Refer to  REMOVAL [12/2023 - ] 

    Result: 

    NG 

    REPLACE ECM. Refer to  REMOVAL [12/2023 - ] 

  7. CHECK HARNESS AND CONNECTOR (FAN WITH MOTOR ASSEMBLY - HYBRID VEHICLE CONTROL ECU) 
    1. Disconnect the A19 fan with motor assembly connector.
    2. Disconnect the B88 hybrid vehicle control ECU connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A19-1 (IGS1) - B88-30 (FANB) Always Below 1 Ω
      A19-1 (IGS1) or B88-30 (FANB) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  8

  8. CHECK HARNESS AND CONNECTOR (HYBRID VEHICLE CONTROL ECU POWER SOURCE) 
    1. Disconnect the B88 hybrid vehicle control ECU connector.
    2. Turn the ignition switch to ON.
    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      B88-6 (+BEG) - Body ground Ignition switch ON 11 to 14 V
      NOTE:

      Make sure to check for and clear DTCs after performing this inspection.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE HYBRID VEHICLE CONTROL ECU. Refer to  REMOVAL [12/2023 - ] 

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

  9. CHECK HARNESS AND CONNECTOR (FAN WITH MOTOR ASSEMBLY - ECM - HYBRID VEHICLE CONTROL ECU) 
    1. Disconnect the A19 fan with motor assembly connector.
    2. Disconnect the A86 ECM connector.
    3. Disconnect the A88 hybrid vehicle control ECU connector.
    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A19-2 (SI) - B86-60 (RFC) Always Below 1 Ω
      A19-2 (SI) - B88-46 (RFC) Always Below 1 Ω
      A19-2 (SI) or B86-60 (RFC) - Body ground Always 10 kΩ or higher
      A19-2 (SI) or B88-46 (RFC) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  10

  10. INSPECT ECM (RFC TERMINAL) 
    1. Disconnect the A19 fan with motor assembly connector.
    2. Disconnect the B88 hybrid vehicle control ECU connector.
    3. Operate the cooling fan motor (fan with motor assembly) using the Active Test function and measure the resistance according to the value(s) in the table below.

      Powertrain > Engine > Active Test 

      Tester Display
      Control the Engine Cooling Fan Duty Ratio

      Standard Resistance

      Tester Connection GTS Operation Specified Condition
      A19-2 (SI) - Body ground Before Active Test (0%) → During Active Test (100%) Before Active Test (0%): Resistance is stable → During Active Test (100%): Resistance fluctuates*

      HINT: 

      *: Using the Active Test, duty control of the transistors in the ECM will be performed. Due to the duty control, resistance of the RFC terminal will be unstable during the Active Test. If the resistance is stable before the Active Test and fluctuates while performing the Active Test, it can be determined that the transistor is operating. If the transistor does not operate during the Active Test, the ECM may be malfunctioning.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE HYBRID VEHICLE CONTROL ECU. Refer to  REMOVAL [12/2023 - ] 

    Result: 

    NG 

    REPLACE ECM. Refer to  REMOVAL [12/2023 - ] 

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