If the reverse lights are out, but the check engine light is on, along with the AC not engaging the compressor clutch, then it is the fuse. If the AC clutch engages and there's no check engine light, chances are good it's the neutral safety switch needing to be cleaned/rebuilt. The @#$%in owners manual incorrectly shows the fuse location as being empty.
Fuse number 10 is for the reverse lights and aforementioned other stuff.
If the fuse is good, then you can try to rebuild/clean your NSS (neutral safety switch) by following this guide:
http://jeepin.com/features/nss/index.asp
A new one is $300 from the stealership, so be careful with it.