[GMcL]

I did it to my S60 when I exported it to Germany:
https://www.volvoforums.org.uk/showp...04&postcount=9

You need to run a cable from the working bulb to the other side of the car. The bulb in the unlit side of the car was already there in my S60. I fitted a relay and used the lead as the switch to the relay then took a live from the rear fuse box to feed the relay to power the bulb.

Do not be tempted to connect the powered lead from the working bulb to the non-powered, this will just trip the control unit.

Edit: This is how I did it...https://www.volvoforums.org.uk/showp...41&postcount=3
Updated link for relay: https://www.halfords.com/motoring/to...tory=undefined