Help!

[hambone83]

I have a 04 Pacifica, AWD, 51K miles.
The ride is wonderful - smooth and very reliable. But facing one small issue.
I have the CD player + 6 DVD changer in dash installed and 7.1 Speaker system with a sub in the rear right side in the back. It has a factory AMP underneath the back floor.

I've never heard the sub work in the past and now I've taken it out and tested the sub w/ 9 volt battery to cehck if its dead, but it responds back. I replaced the amp w/ another working used one and it still doesnt work. I checked the wiring from the amp to the sub and they are good.

What could be wrnog here? Is there a fuse? I checked the fuse box for any blown ones but found nothing bad. Is there something in the CD/DVD player unit? The car lacks some bass and it would be a major bummer if the sub is there and won't ever work. Please help someone!!!

thanks all!