All your parking lights are on one fuse, the 10A Tail, so it's probably not a fuse if half the lights work. LED lighting does not use ballasts, it is simply a light emitting diode. If it's wired in the wrong direction they won't work, but if they worked before then that's not it. The car is split into different circuits and it sounds like you have an open on your one side. I would suggest following the link I have above because it shows you how to narrow the Tail circuit down. Other than that, I would access a DVOM(meter or test light) and see where you have +12v.Well, Just like most of the people on this feed, I am having the same problem w my '02 is300. The difference is that my left side works just fine, although my right side doesn't. The lights that are on my car are LEDs that were on the car when I bought it. Had a couple people check it out seeming to believe it might be the ballast and they are telling me to just get a brand new set of tail lights... There has to be another solution here! Can it really be a fuse or not really seeing as my left one is working?
This is an electrical problem, you don't need to replace your expensive taillight housings. You are getting some bad advice. wouldn't hurt to check the wiring behind it though.