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Home >> Lexus >> 2021 >> GX 460 Luxury >> Repair and Diagnosis >> Accessories & Equipment >> Exterior Lights >> Lighting System (Exterior) (Diagnostic Codes & Circuit Tests) >> Lighting System >> DTC B2439: Headlight LH Circuit; DTC B243A: Headlight RH Circuit [08/2019 - ] >> Description

DTC B2439: Headlight LH Circuit; DTC B243A: Headlight RH Circuit [08/2019 - ]: Description

The No. 1 headlight ECU sub-assembly LH and No. 1 headlight ECU sub-assembly RH internally boost the power supply voltage to ensure a constant supplied current for the Lo/Hi beam LED of their respective headlight.

By monitoring the LED power supply voltage, abnormal current and malfunctions can be detected.

DTC No. Detection Item DTC Detection Condition Trouble Area Note
B2439 Headlight LH Circuit Detection condition: 
  1. All of the following conditions are met:
    • Engine switch on (IG)
    • Low beam headlights on

Malfunction status: 
  • Headlight unit assembly malfunction
  • Open/short in Lo beam circuit

Malfunction duration: 
  1. 1 second or more
  • Headlight unit assembly LH
  • No. 1 headlight ECU sub-assembly LH
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B243A Headlight RH Circuit Detection condition: 
  1. All of the following conditions are met:
    • Engine switch on (IG)
    • Low beam headlights on

Malfunction status: 
  • Headlight unit assembly malfunction
  • Open/short in Lo beam circuit

Malfunction duration: 
  1. 10 seconds or more
  • Headlight unit assembly RH
  • No. 1 headlight ECU sub-assembly RH
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