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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 B243D-29: Low Beam Fan LH Signal Invalid; DTC B243E-29: Low Beam Fan RH Signal Invalid [10/2023 - ] >> Description

DTC B243D-29: Low Beam Fan LH Signal Invalid; DTC B243E-29: Low Beam Fan RH Signal Invalid [10/2023 - ]: Description

The headlight ECU sub-assembly operates the low beam fan to cool the headlight LED unit in order to prevent the headlight LED unit from overheating.

Illuminates the low beam headlights and continuously operates the low beam fan.

The headlight ECU sub-assembly monitors the pulse signals from the FANP terminal when the low beam fans are operating.

HINT: 

If B243D-29 or B243E-29 is output, the headlight ECU sub-assembly performs low beam headlight dimming control.

DTC No. Detection Item DTC Detection Condition Trouble Area Priority
B243D-29 Low Beam Fan LH Signal Invalid Detection condition: 
  1. All of the following conditions are met:
    • The ignition switch is ON
    • Low beam headlights on

Malfunction status: 
  1. Fan speed signals from the low beam fan of less than 1600 rpm are continuously detected

Malfunction duration: 
  1. 120 seconds or more
  • Headlight unit assembly LH
  • Headlight ECU sub-assembly LH
 A
B243E-29 Low Beam Fan RH Signal Invalid Detection condition: 
  1. All of the following conditions are met:
    • The ignition switch is ON
    • Low beam headlights on

Malfunction status: 
  1. Fan speed signals from the low beam fan of less than 1600 rpm are continuously detected

Malfunction duration: 
  1. 120 seconds or more
  • Headlight unit assembly RH
  • Headlight ECU sub-assembly RH
 A
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