Any ideas how to diagnose the issue, best way.
Start with the easiest first - the relays. They are located in the boot/trunk under the cover where the hood/top hydraulic pump is. Using a Jaguar electrical guide, identify which relay relates to the problem window, pull it & clean the contacts, if no different, swap it with the relay from the drivers side rear quarter window & if the passenger side starts working again, you’ve identified a problem relay - especially if the driver’s side stops working!
If the passenger’s side still doesn’t work, there may be a problem with the motor - in which case you have the rear seat & trim panel to remove to access the motor.
HTH.
Andy.
I appreciate the resonse