On the XJ8 there is a nav diagnostic menu which comes up when you press phone + menu fpr 5 seconds. On that system info screen it says "Rear Ent" "fitted".

My cardoes not have the rear entertainment installed, why the head unit still thinks I have one?

Does anyone know what the "software update" button is for?

 

you must have a new disc to operate the software update function, and the rear fitted is because the main wiring harness is in the vehicle already, most of the time in the rear portion of the center console.