U2109-09: Back-up Battery - Component failures: Action

NOTE: This DTC will cause the warning "SOS limited functionality" to be displayed on the instrument cluster

Check the backup battery for poor connection or not connected
Refer to the electrical circuit diagrams and check the telematic control module internal battery circuit for open circuit, high resistance. Repair the wiring harness as necessary
Using the Jaguar Land Rover approved diagnostic equipment, clear the DTCs and perform routine - Test Internal Backup Battery. If the fault persists, install a new telematic control module internal battery