Home › Jaguar › 2017 › XJR Base › Repair and Diagnosis › General Information › DTC Index › Diagnostic Trouble Code (DTC) Index DTC: TELEMATIC Control Module (TCU) -- XJ/X351 › Diagnostic Trouble Code (DTC) Index DTC: Telematic Control Module (TCU) › Description And Operation › TELEMATIC Control Module (TCU) › U2109-09 Back-up Battery - Component failures › Possible Causes