I know on my sedan my trunk light doesn't work period because it's wired into the latch assembly for power/ground and the ground inside the latch assembly is all corroded apparently. So for me, the only way I would be able to get my trunk light working again would be to replace the latch assembly, which isn't a cheap venture... I ended up just getting a little battery-powered sticky LED light from Walmart and attaching it to the roof of my trunk and turning it on and off manually when I need it.
2001 Ford Focus SE, Black - R.I.P.
2001 Ford Focus ZTS, Silver - Hella Dual-Projector Headlamps Painted, Morimoto 5000k 35w H9 kit, eBay CAI