Telematics Control Module Back-Up Battery

WARNING: This page is about a different car, the 2020 Jaguar XE and 2019 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

The back-up battery is integrated into the Telematics Control Module (TCU). The back-up battery is located below a cover which is retained by a screw. The back-up battery contains a single cell that is fully rechargeable.

The back-up battery enables continued operation in the event of a vehicle main power source disconnection, for example:

In a major accident, or
In the case of deliberate action of a thief as part of a vehicle theft attempt.

The back-up battery in the TCU will only be active during an Emergency call (eCall), Breakdown call (bCall) or 'Stolen Vehicle Tracking' session in which the vehicle power supply is disabled. The back-up battery is also required for the Jaguar logistics tracking system when the vehicle is in transit mode.

The ignition off mode may occur before the TCU has sent all of its logistics tracking data to the manufacturer servers. The back-up battery enables the TCU to reliably deliver this data. The TCU is in a pre-activated state when in transit mode.

During the vehicle Pre-Delivery Inspection (PDI) process the TCU is removed from transit mode and switched on to an 'activated state'. When the TCU is removed from transit mode, the telematics system on the vehicle becomes fully active.

The TCU charges the back-up battery when the engine is running. The charging function is controlled and regulated by the TCU software.