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Home >> Lexus >> 2017 >> IS 300 F Sport >> Repair and Diagnosis >> External Pages >> Different car >> Section 4 (Lighting System (Ext) - Diagnostic Codes & Circuit Tests) >> Lighting System >> DTC U0242: Lost Communication With Headlamp Control Module "B" [09/2020 - ] >> Procedure

DTC U0242: Lost Communication With Headlamp Control Module "B" [09/2020 - ]: Procedure

WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 2024 Lexus IS 500, 2024 Lexus IS 350, 2024 Lexus IS 300, 2023 Lexus IS 500, and 2023 Lexus IS 350. However, it is still accessible from the selected car via links, so may be relevant.
  1. CLEAR DTC 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.
    5. Clear the DTCs.

      Body Electrical > HL AutoLeveling > Clear DTCs 

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  2

  2. CHECK FOR DTC 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.
    5. Check for DTCs.

      Body Electrical > HL AutoLeveling > Trouble Codes 

      OK

      DTC U0242 is not output.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [09/2020 - 11/2021]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2021 - 09/2022]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [09/2022 - ] 

    Result: 

    NG 

    See step  3

  3. CHECK HARNESS AND CONNECTOR (HEADLIGHT ECU SUB-ASSEMBLY LH - HEADLIGHT ECU SUB-ASSEMBLY RH) 
    1. Disconnect the A112 headlight ECU sub-assembly LH connector.
    2. Disconnect the A110 headlight ECU sub-assembly RH connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A112-20 (LINL) - A110-20 (LINL) Always Below 1 Ω
      A112-20 (LINL) or A110-20 (LINL) - Body ground Always 10 kΩ or higher

      Result

      Proceed to
      OK
      NG

    Result: 

    NG 

    REPAIR OR REPLACE HARNESS OR CONNECTOR 

    Result: 

    OK 

    See step  4

  4. REPLACE HEADLIGHT ECU SUB-ASSEMBLY RH 
    1. Replace the headlight ECU sub-assembly RH with a new one.

      Refer to REMOVAL [09/2020 - ]

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  5

  5. CLEAR DTC 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.
    5. Clear the DTCs.

      Body Electrical > HL AutoLeveling > Clear DTCs 

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  6

  6. CHECK FOR DTC 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Body Electrical / HL AutoLeveling / Trouble Codes.
    5. Check for DTCs.

      Body Electrical > HL AutoLeveling > Trouble Codes 

      OK

      DTC U0242 is not output.

      Result

      Proceed to
      OK
      NG

    Result: 

    OK 

    END (HEADLIGHT ECU SUB-ASSEMBLY RH WAS DEFECTIVE) 

    Result: 

    NG 

    REPLACE HEADLIGHT ECU SUB-ASSEMBLY LH. Refer to  REMOVAL [09/2020 - ] 

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