Home >> Land Rover >> 2021 >> Defender 110 X >> Repair and Diagnosis (Single Page) >> Quick Lookups >> Common Specs & Procedures >> Diagnostic Trouble Code Index DTC: HVAC Control Module (HVAC) -- Defender/L663 >> Diagnostic Trouble Code Index - DTC: HVAC Control Module (HVAC) (G2400894) >> Description And Operation >> HVAC Control Module (HVAC) >> DTC B1DF4-87: Right Rear Door Armrest Heater - Missing message >> Possible Causes