Home >> Land Rover >> 2021 >> 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 B1087-31: LIN Bus "A" - No signal >> Possible Causes