Home >> Land Rover >> 2021 >> Defender 110 X-Dynamic SE >> Repair and Diagnosis >> Quick Lookups >> Common Specs & Procedures >> 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 B1D03-4B: Right High Beam Circuit - Over temperature >> Possible Causes