Home › Land Rover › 2013 › Range Rover Autobiography › Repair and Diagnosis › Quick Lookups › DTC Index › Diagnostic Trouble Code Index DTC: Telematics Control Module (TCU) -- Range Rover/L405 › Diagnostic Trouble Code Index DTC: Telematics Control Module (TCU) › Description And Operation › DTC U2109-91: Back-up Battery - Parametric › Possible Causes