I just purchased a 2007 Grand Caravan. It has the CD tape deck, 6 DVD changer and video screen. edit: It looks like I also have a sub-woofer in the back of the van on the passenger side.

The radio and DVD player power up fine, you can tune to a radio station and it will give you the station ID. The problem is when you turn up the volume, there is no sound at all. This is the same no matter what input I use.

So far, I have checked all the fuses under the hood. There were no blown fuses.

Could it be my amp? How do I tell if I have an amp? And if I do, how can I test it?
I'd rather no replace the stock stereo with an aftermarket radio.

Any ideas on where to start trouble shooting?