I added an AUX port to my factory radio using the CD changer control harness. I took an older write up from smunns (grey goose wj) and updated the info a bit. I have a 99 WJ and his write up was for the 02-04 WJ's. The radio/cd connector/wiring is a bit different between the 99-01 and 02-04's. I took his wiring diagram and updated it so the people with a 99-01 would have a quick reference sheet. Works perfectly, I spent $10 and about an hour to complete.
I won't rewrite his article, you can find it here...
http://www.jeepforum.com/forum/f197/gray-goose-build-thread-1089523/#post9992383
You'll need the radio shack stereo adapter... $3
http://www.radioshack.com/product/index.jsp?productId=2103451
and a 3.5mm Male to Female 6'-8' extension. $6
Using his info as a guide, I wired the aux adapter directly to the back of the CD connector harness and plugged in the 8' aux cord extension to it there. It is secured and hidden behind the radio. I ran the aux cord extension under the console up near the seat belt harness, the excess length is wrapped up and tucked behind dash at the front of console. From there, using a standard male/male aux cord I can plug in whenever I want to play my iphone/ipod. My thought was, if a connector or cable goes bad, I would like to be able to replace it easily... I also didn't want to mount the aux adapter permanently to the dash since I'm sure I'll eventually upgrade the radio. Just press CD and voila...music from the phone.
Here's the updated wiring diagram that shows both WJ models...
Testing the connection...
Soldered...(thats just black tape between the connections)
Taped and Secured...
finished...
also a good shot of all that fake plastic wood grain I covered up with plasti dip!
Hope it helps someone else... super easy and cheap if your just needing an aux port.