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Home >> Lexus >> 2024 >> RX 500h >> Repair and Diagnosis >> External Pages >> Different car >> Section 83 (Heating / Air Conditioning System - Diagnostic Codes (1 Of 3)) >> AIR CONDITIONING SYSTEM (for PHEV Model) >> DTC B14AB-7F: Heating Three-way Valve Actuator Stuck Off [08/2023 - ] >> Procedure

DTC B14AB-7F: Heating Three-way Valve Actuator Stuck Off [08/2023 - ]: Procedure

WARNING: This page is about a different car, the 2025 Lexus RX 450h+ and 2024 Lexus RX 450h+. However, it is still accessible from the selected car via links, so may be relevant.
  1. PERFORM ACTIVE TEST USING GTS 
    1. Check the operation by referring to the table below.

      Body Electrical > Air Conditioner > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      Heater Valve This test changes the heater valve to Open/Half/Close.
      (Heating three-way valve (heater water valve assembly))      		 Close: Valve Close Position
      Half: Valve Middle Position
      Open: Valve Open Position      		 Operate with the ignition switch ON (READY).

      Body Electrical > Air Conditioner > Active Test 

      Tester Display
      Heater Valve

      Body Electrical > Air Conditioner > Data List 

      Tester Display Measurement Item Range Normal Condition Diagnostic Note
      Heating Three-way Valve Target Position Target opening angle of heating three-way valve (heater water valve assembly) 0 to 100 % Target opening angle Heating three-way valve (heater water valve assembly) circuit malfunction
      • Combination: 0%
      • Single: 100%
      Heating Three-way Valve Actual Position Actual opening angle of heating three-way valve (heater water valve assembly) 0 to 100 % Actual opening angle following the target opening angle Heating three-way valve (heater water valve assembly) circuit malfunction
      • Combination: 0%
      • Single: 100%
      Heater Valve Operation condition of heating three-way valve (heater water valve assembly) Close / Half / Open
      • Close: Target angle 100% (Single)
      • Half: Target angle 50%
      • Open: Target angle 0% (Combination)
      		 Heating three-way valve (heater water valve assembly) circuit malfunction

      Body Electrical > Air Conditioner > Data List 

      Tester Display
      Heating Three-way Valve Target Position
      Heating Three-way Valve Actual Position
      Heater Valve

      OK

      Heating three-way valve (heater water valve assembly) is operated.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to  REMOVAL [10/2022 - ] 

    Result: 

    NG 

    See step  2

  2. CHECK HARNESS AND CONNECTOR (HEATING THREE-WAY VALVE (HEATER WATER VALVE ASSEMBLY) - AIR CONDITIONING AMPLIFIER ASSEMBLY) 

    Pre-procedure1

    • Disconnect the q4 heating three-way valve (heater water valve assembly) connector.
    • Disconnect the C50 air conditioning amplifier assembly connector.
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      q4-2 (+) - C50-20 (MP2+) Always Below 1 Ω Ω
      q4-6 (-) - C50-21 (MP2-) Always Below 1 Ω Ω
      q4-5 (WVO) - C50-2 (S5-4) Always Below 1 Ω Ω
      q4-4 (WVS) - C50-6 (PO1) Always Below 1 Ω Ω
      q4-3 (SG) - C50-1 (SG-6) Always Below 1 Ω Ω
      q4-2 (+) or C50-20 (MP2+) - Other terminals and body ground Always 10 kΩ or higher kΩ
      q4-6 (-) or C50-21 (MP2-) - Other terminals and body ground Always 10 kΩ or higher kΩ
      q4-5 (WVO) or C50-2 (S5-4) - Other terminals and body ground Always 10 kΩ or higher kΩ
      q4-4 (WVS) or C50-6 (PO1) - Other terminals and body ground Always 10 kΩ or higher kΩ
      q4-3 (SG) or C50-1 (SG-6) - Other terminals and body ground Always 10 kΩ or higher kΩ

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • None

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  3

  3. CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY 

    Pre-procedure1

    • Disconnect the q4 heating three-way valve (heater water valve assembly) connector.
    • Measure the voltage according to the value(s) in the table below.
      GTY1207336Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Air Conditioning Amplifier Assembly)      		 - -

      Standard Voltage

      Tester Connection Condition Specified Condition Result
      C50-2 (S5-4) - Body ground Ignition switch ON 4.75 to 5.25 V V
      C50-6 (PO1) - Body ground Ignition switch ON 4.75 to 5.25 V V
    • Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition Result
      C50-1 (SG-6) - Body ground Always Below 1 Ω Ω

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • None

    Result: 

    NG 

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to  REMOVAL [10/2022 - ] 

    Result: 

    OK 

    See step  4

  4. PERFORM ACTIVE TEST USING GTS 

    Pre-procedure1

    • Disconnect the q4 heating three-way valve (heater water valve assembly) connector.
    • Perform the Active Test according to the display on the GTS.

      Body Electrical > Air Conditioner > Active Test 

      Tester Display Measurement Item Control Range Diagnostic Note
      Heater Valve This test changes the heater valve to Open/Half/Close.
      (Heating three-way valve (heater water valve assembly))      		 Close: Valve Close Position
      Half: Valve Middle Position
      Open: Valve Open Position      		 Operate with the ignition switch ON (READY).

      Body Electrical > Air Conditioner > Active Test 

      Tester Display
      Heater Valve
    • Measure the voltage according to the value(s) in the table below.
      GTY1207335Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *a Component with harness connected
      (Air Conditioning Amplifier Assembly)      		 - -

      Standard Voltage

      Tester Connection Condition Specified Condition
      C50-20 (MP2+) - Body ground Perform Active Test and select Open (Combination) → Close (Single) item Below 1 V → 11 to 14V → Below 1 V
      C50-21 (MP2-) - Body ground Perform Active Test and select Close (Single) → Open (Combination) item Below 1 V → 11 to 14V → Below 1 V

      Result

      Proceed to
      OK
      NG

    Post-procedure1

    • None

    Result: 

    OK 

    REPLACE HEATING THREE-WAY VALVE (HEATER WATER VALVE ASSEMBLY). Refer to  REMOVAL [08/2023 - ] 

    Result: 

    NG 

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to  REMOVAL [10/2022 - ] 

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