Ive done some searching and havent found anything that can answer this question:

what drives the factory navigation system. Is it a stand alone unit or does it interface with the stock head unit?

 

I am in the process now of replacing it. Pioneer has a Nav Head unit that fits in the upper screen area, and my stereo guy did a preliminary rip apart, to see what was required. The ML head unit controls the door, and the voice for the Nav, and has the video output to the screen. He is putting the Pioneer in between the ML head and factory amp to retain ML controls. The pioneer unit has bluetooth, Navi, and Ipod controls with video. In short, it would take a lot of rewiring to get the Nav working without the ML.

 

they are integrated. if you want to replace one, the easiest thing to do would be to replace both. i've heard of some people relocating the stock stereo to the trunk in order to keep the navigation when they replace the head unit. personally, i'd just leave it alone. the stock head unit is good. the speakers are crap. replace those and the amps and you'll get much better audio if that's what you're after.

 

thanks guys. is there a way to wire a new head unit to be able to utilize video on stock screen?

 

NavTool is the interface that lets you have an aux input (2, in fact) for the factory screen.

One input is dedicated to backup camera duty and is activated when the car it put in reverse...the other input is activated by a toggle switch...which can be installed in one of various locations in the car.

The NavTool just gives you composite inputs (single RCA jack)...not the best but, it works for most things.

You can find them on eBay and they sometimes have a group-buy going on here as well. If you get one from eBay, make sure you get the one with the wiring harness that's specific to the SC430. They sell a "flying lead" version...you DON'T want that!.