06 Charger Won't Start Sometimes - Going Into Limp Mode

I have a 2006 Charger R/T. My car used to not start (even thought the battery, starter, and alternator was good). I had it fixed, and the problem seemed to be electrical. However after that, it would always start, but would go into "limp mode". I let it sit for two days, and the limp mode disappeared. However, it will only start on occasion. It won't start after about 30 mins after use. It won't start for a few hours. All electrics work fine, it just won't even attempt to crank. Try to start it later, it will work fine. Even though the check engine light was NOT on, I was able to pull three codes out of it: U0100, U0103, P0700. I did have to replace the notorious "pink thingy", but everything (should be) connected fine.