Home › Land Rover › 2021 › Defender 110 › Repair and Diagnosis › General Information › Specifications Index › 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 U3000-04: Control Module - System internal failures › Possible Causes