Originally Posted by MattP725

You still haven't addressed if you checked the head unit... there is a bass control setting... make sure it is all the way up (to see if it works). If that doesn't do it, you will find a ton of them for sale I'm sure.

I'd start by replacing the sub and then move to the amp and the head unit after that... it should be one of the three unless a wire is broken.

Otherwise if you are handy or have an electrician local, have them check the voltage going to the sub.