Home >> Land Rover >> 2021 >> Defender 110 X-Dynamic HSE >> Repair and Diagnosis >> Quick Lookups >> Common Specs & Procedures >> Diagnostic Trouble Code Index DTC: TELEMATIC Control Unit Module (TCU) -- Defender/L663 >> Diagnostic Trouble Code Index - DTC: TELEMATIC Control Unit Module (TCU) (G2400918) >> Description And Operation >> TELEMATIC Control Unit Module (TCU) >> DTC U2109-09: Back-up Battery - Component failures >> Possible Causes