Pioneer car stereo/audio fake or genuine?

A link to the product would have helped...

But no. There's no secret special thing authentic Pioneer units have that knock offs don't. Secondly, although there's plenty of cheap Chinese generic stereos on the internet, I don't think there's too many actually faking to be Pioneer. Most of the cheap junk just doesn't have a name on it. All Pioneer's will have the Pioneer name and nearly 100% of them have the model number printed on the face in small print somewhere. (Think all their current models do, with exception of the AppRadio)

If you're really worried about it, just do your homework on the unit, make sure the seller has a lot of positive feedback, and buy from someone in the US. Or just buy from Amazon or Sonicelectronix. Usually same price as eBay anyway...

Once you know what you want, order it from Crutchfield.