Home >> Jaguar >> 2017 >> XF S, AWD >> Repair and Diagnosis >> Quick Lookups >> DTC Index >> Diagnostic Trouble Code Index DTC: TELEMATIC Control Module (TCU) -- XF/X260 >> Diagnostic Trouble Code Index DTC: Telematic Control Module (TCU) >> Description And Operation >> Telematics Control Module (TCU) >> DTC U2109-91: Back-up Battery - Parametric >> Possible Causes