Where would be the easiest place to hook up the ILL wire. No connection in the original harness, but I want it to work. I have and use the Auto lights switch in case that matters.

Thanks

u can tap the illumination wire off the parking lights wire on the car. the parking lights wire 4 ur car is brown and in the driver's kick panel. just extend a line off the pioneer wire harness n run it to the kick panel.

The junction box next to the driver side kick panel has a illumination wire that also comes on with the auto lights. It's in the top row of plugs second socket from the left in the bottom left pin. I have a 2006 silverado LS model and this method worked for me. Since it's a different model, you might wanna check it first with a voltmeter.
I got this info from the "the12volt" forum so I gotta give credit where it's due.