Home › Land Rover › 2020 › Defender 110 S › Repair and Diagnosis › General Information › Specifications Index › Diagnostic Trouble Code Index DTC: Headlamp Control Module (HCM) -- Defender/L663 › Diagnostic Trouble Code Index - DTC: Headlamp Control Module (HCM) (G2423982) › Description And Operation › Headlamp Control Module (HCM) › DTC B10F3-13: Left front position light - Circuit open › Possible Causes