i'm going through this too. if u fix ur grounds and the lights still dont work its ur tail light failure sensor. its the little yellow box that is rite under the left tail light. i called the dealer earlier today (cus autozone cant get it) and it only costs a cool 275$. so me and my dad temporarily fixed it by putting a metal wire (paper clip) into two if the wire connections(i dont remember the colors but i can find out if u want). the downside to this is the the tree light no longer works. this is only a temporary fix of course but its something to think about if u don't hav 300$ laying around, hahah. or u could see if someone is selling it on here......