Replacement for 02 Tahoe head unit

Yea class 2 only started with the big suvs and trucks in 03.  The On-Star in and of itself is a pain and depending on whether or not your factory radio has RDS, you might not even be able to interface with the On-Star system.  Might want to ask Karl from PAC about that, I'm sure he knows the answer.

Do you still want to be able to use the rear seat controls?  Or does that not really matter to you?  If it doesn't you can just hook up an aftermarket deck but you'll lose that rear seat functionality.  I am not aware of any way to interface an aftermarket deck with these rear seat controls, although I guess it might be possible but I've never heard of it being done with aftermarket decks.

As for a rear seat entertainment system, there are a few different ways to hook up the audio.   A lot of times people are just adding on to a factory system, in which case you usually use an FM modulator.  PAC just came out with a new adapter that adds traditional RCA inputs to a factory GM radio, so that's what you should use if you keep the factory deck and add on a mobile video system or something like that.

Best way to hook up the audio with an aftermarket deck would be to get an auxilliary input adapter for whatever brand head unit you have (all the manufacturers have them nowadays).  Basically what these do is add RCA audio inputs to the back of your aftermarket head unit.  Usually they eliminate the cd changer port but some of them have additional models that cost about twice as much but retain the extra changer port.

Again, I'm not sure how all this stuff would interface with the rear audio controls or if it's even possible.  Just out of curiosity, do you have the Bose system in this vehicle?  And what about the RDS? 

You'll know your vehicle has RDS if it automatically displays some station call names in addition to their frequencies.  RDS stands for Radio Data System and the way I understand it, it's basically a way that some stations send additional info to your radio like call names.  I've heard that in some places they'll also give you traffic alerts if there's an accident ahead.

I always thought that just because a system has RDS, doesn't necessarily mean the vehicle has the Class II wiring.  In fact I was working on a 2003 blazer xtreme a couple days ago and was gonna do a radio in it.  It had the RDS system but once I took the factory radio out, the door chimes still worked, so I'm assuming that it did not have the Class II system in it.

Where's the alternator noise coming from?  The sub?  The speakers?  Any of them in particular?