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.
Courtesy of JAGUAR LAND ROVER NORTH AMERICA, LLC
The BCM/GWM controls the operation of the seatbelt warning indicator with a HS CAN powertrain systems bus message to the IC (Instrument Cluster).