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Home >> Lexus >> 2025 >> NX 350 Base >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Headlights >> Lighting System (W/ Level Control) - Diagnostic Codes (1 Of 2) >> LIGHTING SYSTEM (w/ Automatic Headlight Beam Level Control System) >> DTC B242C-04: Headlight Control Module (Sub) System Internal Failure; DTC B242D-04: Headlight Control Module (Main) System Internal Failure [03/2022 - ] >> Procedure
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DTC B242C-04: Headlight Control Module (Sub) System Internal Failure; DTC B242D-04: Headlight Control Module (Main) System Internal Failure [03/2022 - ]: Procedure

  1. CLEAR DTC 
    1. Clear the DTCs.

      Body Electrical > Headlight Control (Sub) > Clear DTCs 

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  2

  2. CHECK FOR DTC 

    Pre-procedure1

    1. Turn ignition switch to ON.
    2. Wait for at least maximum 15 minutes.

      Procedure1

    3. Check for DTCs.

      Body Electrical > Headlight Control (Sub) > Trouble Codes 

      Result

      Result Proceed to
      B242C-04 is not output A
      B242C-04 is output (except TMMC Made) B
      B242C-04 is output (for TMMC Made) C

      Post-procedure1

    4. None

    Result: 

    REPLACE HEADLIGHT ECU SUB-ASSEMBLY RH. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    REPLACE HEADLIGHT ASSEMBLY RH 

    for LED Type Turn Signal Light: Refer to REMOVAL [11/2021 - ]

    for Bulb Type Turn Signal Light: Refer to REMOVAL [11/2021 - ]

    Result: 

    See step  3

  3. CLEAR DTC 
    1. Clear the DTCs.

      Body Electrical > Headlight Control > Clear DTCs 

      Result

      Proceed to
      NEXT

    Result: 

    NEXT 

    See step  4

  4. CHECK FOR DTC 

    Pre-procedure1

    1. Turn ignition switch to ON.
    2. Wait for at least maximum 15 minutes.

      Procedure1

    3. Check for DTCs.

      Body Electrical > Headlight Control > Trouble Codes 

      Result

      Result Proceed to
      B242D-04 is not output A
      B242D-04 is output (except TMMC Made) B
      B242D-04 is output (for TMMC Made) C

      Post-procedure1

    4. None

    Result: 

    USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2021 - ] 

    Result: 

    REPLACE HEADLIGHT ECU SUB-ASSEMBLY LH. Refer to  REMOVAL [11/2021 - ] 

    Result: 

    REPLACE HEADLIGHT ASSEMBLY LH 

    for LED Type Turn Signal Light: Refer to REMOVAL [11/2021 - ]

    for Bulb Type Turn Signal Light: Refer to REMOVAL [11/2021 - ]