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Home >> Lexus >> 2021 >> LS 500h RWD >> Repair and Diagnosis >> Accessories & Equipment >> Seats >> Seat Heater System - Diagnostic Codes & Symptom Tests (1 Of 2) >> Seat Heater System >> Seat Heater for Front Left Seat does not Operate [10/2017 - 10/2020] >> Procedure

Seat Heater for Front Left Seat does not Operate [10/2017 - 10/2020]: Procedure

  1. CLEAR DTC 
    1. Clear the DTCs.

      Refer to DTC CHECK / CLEAR [10/2017 - ]

      Body Electrical > Air Conditioner > Clear DTCs 

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  2

  2. CHECK FOR DTC 
    1. Check for DTCs.

      Refer to DTC CHECK / CLEAR [10/2017 - ]

      Body Electrical > Air Conditioner > Trouble Codes 

      OK

      DTC B14C1 is not output.

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    GO TO DIAGNOSTIC TROUBLE CODE CHART. Refer to  DIAGNOSTIC TROUBLE CODE CHART [10/2017 - ] 

    Result: 

    OK 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (SEAT HEATER CONTROL SUB-ASSEMBLY LH - BATTERY) 
    1. Disconnect the Q31 seat heater control sub-assembly LH connector.
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Switch Condition Specified Condition
      Q31-3 (IG) - Body ground Power switch on (IG) 11 to 14 V
      Power switch off Below 1 V
      Q31-1 (+B1) - Body ground Power switch off 11 to 14 V
      Q31-8 (+B2) - Body ground Power switch off 11 to 14 V

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. INSPECT SEPARATE TYPE FRONT SEAT CUSHION COVER LH 
    1. Remove the separate type front seat cushion cover LH.

      Refer to REMOVAL [10/2017 - 09/2018] , or refer to REMOVAL [09/2018 - 10/2020]

    2. Inspect the separate type front seat cushion cover LH.

      Refer to INSPECTION [10/2017 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE SEPARATE TYPE FRONT SEAT CUSHION COVER LH. Refer to  REMOVAL [10/2017 - 09/2018]  , or refer to  REMOVAL [09/2018 - 10/2020] 

    Result: 

    OK 

    See step  5

  5. INSPECT SEPARATE TYPE FRONT SEATBACK COVER LH 
    1. Remove the separate type front seatback cover LH.

      Refer to REMOVAL [10/2017 - 09/2018] , or refer to REMOVAL [09/2018 - 10/2020]

    2. Inspect the separate type front seatback cover LH.

      Refer to INSPECTION [10/2017 - ]

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPLACE SEPARATE TYPE FRONT SEATBACK COVER LH. Refer to  REMOVAL [10/2017 - 09/2018]  , or refer to  REMOVAL [09/2018 - 10/2020] 

    Result: 

    OK 

    See step  6

  6. CHECK HARNESS AND CONNECTOR (SEPARATE TYPE FRONT SEAT CUSHION COVER LH - SEAT HEATER CONTROL SUB-ASSEMBLY LH AND BODY GROUND) 
    1. Disconnect the Q36 separate type front seat cushion cover LH connector.
    2. Disconnect the Q31 seat heater control sub-assembly LH connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      Q36-6 - Q31-10 (E) Always Below 1 Ω
      Q36-6 or Q31-10 (E) - Other terminals and body ground Always 10 kΩ or higher
      Q36-1 - Q31-7 (Heater Output 1) Always Below 1 Ω
      Q36-1 or Q31-7 (Heater Output 1) - Other terminals and body ground Always 10 kΩ or higher
      Q36-3 - Q31-12 (Heater Output 2) Always Below 1 Ω
      Q36-3 or Q31-12 (Heater Output 2) - Other terminals and body ground Always 10 kΩ or higher
      Q36-2 - Body ground Always Below 1 Ω

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  7

  7. CHECK HARNESS AND CONNECTOR (SEPARATE TYPE FRONT SEAT CUSHION COVER LH - AIR CONDITIONING AMPLIFIER ASSEMBLY) 
    1. Disconnect the Q36 separate type front seat cushion cover LH connector.
    2. Disconnect the G63 and G64 air conditioning amplifier assembly connectors.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      Q36-4 - G63-17 (TSL) Always Below 1 Ω
      Q36-4 or G63-17 (TSL) - Other terminals and body ground Always 10 kΩ or higher
      Q36-5 - G64-3 (SG-4) Always Below 1 Ω
      Q36-5 or G64-3 (SG-4) - Other terminals and 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 (SEAT HEATER CONTROL SUB-ASSEMBLY LH - AIR CONDITIONING AMPLIFIER ASSEMBLY) 
    1. Disconnect the Q31 seat heater control sub-assembly LH connector.
    2. Disconnect the G63 air conditioning amplifier assembly connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      Q31-4 (PWM) - G63-15 (SHD+) Always Below 1 Ω
      Q31-4 (PWM) or G63-15 (SHD+) - Other terminals and body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  9

  9. REPLACE SEAT HEATER CONTROL SUB-ASSEMBLY LH 
    1. Temporarily replace the seat heater control sub-assembly LH with a new or known good one.

      Refer to REMOVAL [10/2017 - 09/2018] , or refer to REMOVAL [09/2018 - 10/2020]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  10

  10. CHECK SEAT HEATER OPERATION 
    1. Check the seat heater.

      Refer to OPERATION CHECK [10/2017 - 10/2022]

      OK

      The seat heater operates normally.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    END (SEAT HEATER CONTROL SUB-ASSEMBLY LH WAS DEFECTIVE) 

    Result: 

    NG 

    REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY. Refer to  REMOVAL [10/2017 - ]