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Home >> Toyota >> 2021 >> Highlander LE, 4WD >> Repair and Diagnosis >> Body & Frame >> Seats >> Seat Heater System - Diagnostic Codes & Symptom Tests >> Seat Heater System >> DTC B14B5: Lost Communication with Front Seat Temperature Adjustment Switch LIN [12/2019 - 11/2023] >> Procedure

DTC B14B5: Lost Communication with Front Seat Temperature Adjustment Switch LIN [12/2019 - 11/2023]: Procedure

  1. CLEAR DTC 
    1. Clear the DTCs.

      Body Electrical > Air Conditioner > Clear DTCs 

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  2

  2. CHECK FOR DTC 
    1. Check for DTCs.

      Body Electrical > Air Conditioner > Trouble Codes 

      OK

      DTC B14B5 is not output.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2019 - ] 

    Result: 

    NG 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (IG POWER SUPPLY - FRONT SEAT HEATER SWITCH (AIR CONDITIONING CONTROL ASSEMBLY) - GROUND) 
    1. Disconnect the H27 front seat heater switch (air conditioning control assembly) connector.
      GTY848142Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *A for 12.3 Inch Display
      *B for 8 Inch Display
      *a Front view of wire harness connector
      (to Front Seat Heater Switch (Air Conditioning Control Assembly))
    2. Measure the voltage and resistance according to the value(s) in the table below.

      Standard Voltage

      FOR 12.3 INCH DISPLAY

      Tester Connection Condition Specified Condition
      H27-4 (IG+) - Body ground Ignition switch ON 11 to 14 V
      H27-4 (IG+) - Body ground Ignition switch off Below 1 V
      FOR 8 INCH DISPLAY

      Tester Connection Condition Specified Condition
      H27-6 (IG+) - Body ground Ignition switch ON 11 to 14 V
      H27-6 (IG+) - Body ground Ignition switch off Below 1 V

      Standard Resistance

      FOR 12.3 INCH DISPLAY

      Tester Connection Condition Specified Condition
      H27-8 (E) - Body ground Always Below 1 Ω
      FOR 8 INCH DISPLAY

      Tester Connection Condition Specified Condition
      H27-10 (GND) - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. CHECK HARNESS AND CONNECTOR (AIR CONDITIONING AMPLIFIER ASSEMBLY - FRONT SEAT HEATER SWITCH (AIR CONDITIONING CONTROL ASSEMBLY)) 
    1. Disconnect the H62 air conditioning amplifier assembly connector.
    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      FOR 12.3 INCH DISPLAY

      Tester Connection Condition Specified Condition
      H62-7 (LIN1) - H27-3 (LIN1) Always Below 1 Ω
      H62-7 (LIN1) or H27-3 (LIN1) - Body ground Always 10 kΩ or higher
      FOR 8 INCH DISPLAY

      Tester Connection Condition Specified Condition
      H62-7 (LIN1) - H27-8 (LIN1) Always Below 1 Ω
      H62-7 (LIN1) or H27-8 (LIN1) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  5

  5. INSPECT AIR CONDITIONING AMPLIFIER ASSEMBLY 
    1. Connect the H62 air conditioning amplifier assembly connector.
      GTY550876Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Turn the ignition switch to ON.
    3. Using an oscilloscope, check the waveform.

      OK

      Waveform is similar to that shown in the illustration.

      Item Content
      Terminal No. H62-7 (LIN1) - Body ground
      Tool Setting 2 V/DIV., 20 ms./DIV.
      Condition Ignition switch ON

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

    Result: 

    OK 

    See step  6

  6. INSPECT FRONT SEAT HEATER SWITCH (AIR CONDITIONING CONTROL ASSEMBLY) 
    1. Connect the H27 front seat heater switch (air conditioning control assembly) connector.
      GTY908766Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      *A for 12.3 Inch Display
      *B for 8 Inch Display
      *a Component with harness connected
      (Front Seat Heater Switch (Air Conditioning Control Assembly))
    2. Turn the ignition switch to ON.
    3. Using an oscilloscope, check the waveform.
      Item Content
      Terminal No. H27-3 (LIN1)*1 - Body ground
      H27-8 (LIN1)*2 - Body ground
      Tool Setting 2 V/DIV., 20 ms./DIV.
      Condition Ignition switch ON
      1. *1: for 12.3 Inch Display
      2. *2: for 8 Inch Display

      OK

      Waveform is similar to that shown in the illustration.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to  REMOVAL [12/2019 - 10/2022]  , or refer to  REMOVAL [10/2022 - 11/2023] 

    Result: 

    NG 

    REPLACE FRONT SEAT HEATER SWITCH (AIR CONDITIONING CONTROL ASSEMBLY). Refer to  REMOVAL [12/2019 - ] 

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