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Home >> Lexus >> 2021 >> LS 500 Base, RWD >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Exterior Lights >> Lighting System (Ext) - Diagnostic Codes (2 Of 3) >> Lighting System >> DTC B2439: Headlight LH Circuit; DTC B243A: Headlight RH Circuit [12/2017 - 10/2023] >> Description

DTC B2439: Headlight LH Circuit; DTC B243A: Headlight RH Circuit [12/2017 - 10/2023]: Description

The headlight ECU sub-assembly supplies internally boosted voltage to the LED so that the current supplied to the LED is always maintained at a constant value.

These DTCs are also output when the headlight ECU sub-assembly detects malfunctions while monitoring the applied voltage.

DTC No. Detection Item DTC Detection Condition Trouble Area DTC Output from Note
B2439 Headlight LH Circuit Detection condition: 
  1. Engine switch on (IG), low beam headlights illuminated

Malfunction status: 
  • LED (LED) malfunction
  • Open/short in LED (LEG) circuit

Malfunction duration: 
  1. 10 seconds or more
  • Headlight unit assembly LH
  • Headlight ECU sub-assembly LH
AFS -
B243A Headlight RH Circuit Detection condition: 
  1. Engine switch on (IG), low beam headlights illuminated

Malfunction status: 
  • LED (LED) malfunction
  • Open/short in LED (LEG) circuit

Malfunction duration: 
  1. 10 seconds or more
  • Headlight unit assembly RH
  • Headlight ECU sub-assembly RH
AFS (Sub) -