Home >> Land Rover >> 2020 >> Defender 110 First Edition >> 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 B146B-4B: Left Front Side Marker Lamp - Over temperature >> Possible Causes