If the stereo in 2002 Navi has no bass and all trebile what is the deal speakers are fine and don't crackle just zero bass?

It may very well be the subwoofer in the back of the truck passenger side panel, could be the amp or the subwoofer is toast. I had to replace one on my 98 gator, but it was noticeably blown. It requires taking off the entire rear side panel. The subwoofer is bolted on through the backside of the bass box so the only way to get to it is a full tearout. hope this points you in a direction. There are other articles on here about replacing the woofer&amp.