I've spent hours searching this and other forums for an answer, with no luck. Are the HU/HVAC Control units from later model G35s (2003.5 - 2004) compatible with the early 2003s?

My wife has an early 2003 "Doggie Door" G35 sedan, with a HU/HVAC unit that is not equipped with a SAT button. As seems to be customary, we have experienced the dreaded "CD ERROR FO", and now the AC won't blow cold air. She has also on occasion had the common issue with non-responsive controls and the (warm) air blowing full blast.

I have purchased two seperate radios (from eBay) that were pulled from later model 2003.5 - 2004 G35s, and neither unit has worked. besides the SAT button, the units appear identical, but have different model numbers.

However, the pigtail lead coming from the faceplate has a black (ground) wire included - could it be that I need to modify the harness to make it work?

Thanks so much in advance for your input.