does the rest of the spreakers play? if so its not fuse related.. u talking the deck speakers or door? look for the amp in trunk uptop/underside. make sure no mores came off 6x8 or 6x9.. id unplug the gray plug out of amp and plug it back ingood, and tight, once i have seen 2 wires to each deck speaker.
This statement is based on what?
The amp for the subs does have its own fuse. While it's unlikely that this is a fuse, if fuse F4.18 (trunk fuse box) is blown, then it would stop the subs, and only the subs from working. (Unless he had THX navigation, then it would stop the door speakers too.)