Home › Jaguar › 2013 › XJ Base, AWD › Repair and Diagnosis › Quick Lookups › 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) › U2109-91 Back-up Battery - Parametric › Possible Causes