Home >> Land Rover >> 2019 >> Range Rover SVAutobiography >> Repair and Diagnosis >> Quick Lookups >> Common Specs & Procedures >> Diagnostic Trouble Code Index DTC: Automatic Temperature Control Module (ATCM) -- Range Rover/L405 >> General Information >> Description And Operation >> Diagnostic Trouble Code Index - DTC: Automatic Temperature Control Module (ATCM) (G2164849) >> DTC B1421-4B: Left Front Cooled/Heated Seat Thermal Electric Device #2 - Over temperature >> Possible Causes