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

WARNING: This page does not describe the selected car, but rather 12 other vehicles, including the 2017 Jaguar XJR, 2017 Jaguar XJ, 2016 Jaguar XJR, 2016 Jaguar XJ, and 2015 Jaguar XJR. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Following an emergency call or stolen vehicle tracking alert, a new telematics control module internal battery must be installed before this DTC can be cleared.

Check backup battery for poor connection or not connected
Refer to the electrical circuit diagrams and check the telematics control module internal battery circuit for open circuit, high resistance
Using the manufacturer approved diagnostic system, clear the DTCs and perform routine - Test Internal Backup Battery (0x040C). If the fault persists, install a new telematics control module internal battery. Using the manufacturer approved diagnostic system, reset the non rechargeable battery power level following the backup battery replacement process