Home >> Land Rover >> 2021 >> Defender 110 S >> Repair and Diagnosis >> 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 B1DF8-4B: Left Rear Calf Rest Heater - Over temperature >> Possible Causes