Here is the link with the technical info you need, cheez:
http://www.jeeppatriot.com/forum/showthread.php?p=29193#post29193
Now, I understand that this info won't really help if you have no idea what they're talking about. When I first started looking to upgrade, I was trying to find an explanation in plain English, too, but it just doesn't seem to exist...so after several more hours of research, I think I figured it out. Let me see if I can explain it so you don't have to spend the time, too.
The problem here is that in late model Chryslers, Jeeps, and some other vehicles, the manufacturer has wired the stock stereo in a way that it's integrated in the vehicle's electrical/computer system. In other words, there aren't just power and speaker wires running to and from the stereo, like in the old days. The stereo is now wired into the "nerve system" of the vehicle (called the CAN-BUS in the Jeeps), so it can "help" by playing warning tones, display vehicle info, work with the steering wheel controls, etc. Cynics would also say that manufacturers have done this to try to make you buy *their* stereo upgrades instead of having aftermarket work done.
So the bad news is that you can't just rip out the stock stereo, screw a coupla wires into your new pioneer, and be good to go. You'll probably lose some functionality...which could or could not be important to your vehicle/radio operation, depending on what features you have.
The good news is that third parties make adapters that allow you to retain functions and let your aftermarket stereo integrate into the CAN-BUS. It makes it more complicated, but at least it's still possible.
My understanding is that the first wire harness option listed at that link will allow you to retain pretty much all functionality. It requires an extra couple of wiring harnesses, though: you've gotta get one for the steering wheel controls, then you've gotta get the actual steering wheel control adapter, and you've gotta get the radio wiring harness. I think the first option only lists the steering wheel control adapter and the radio wiring harness, so you need to find the steering wheel control harness, as well.
Now, the problem (for me) with the steering wheel control adapters is that they work by taking the signal from your steering wheel controls and using it to send an infrared signal to the infrared receiver on your aftermarket stereo. In other words, you can't just run a wire from the adapter to some input on the back of your stereo, out of sight, out of mind. So, first, you have to make sure your new stereo has an infrared remote control. And, second, you have to run the wire with the infrared broadcaster on the end somewhere in your console area so that it has a clear line of sight to your stereo's infrared receiver. I don't really want to clutter up my console with another wire and the IR button, especially when the radio is so close to the steering wheel in the Patriot anyway, so I think I'm gonna skip this option.
That means I'm planning to go with the second option. It allows you to retain your accessory power and illumination of the stereo in integrating it into the CAN-BUS. I've found places on the internet you can get it for about $50...just search for the part #.
I hope this helps you understand the situation a bit better. I was trying to find this type of explanation when I first started looking to upgrade several months ago, and finally, thanks to Jim and some others on this site, I was able to at least find the info to educate myself on it.
