Well ... dumb question, but I assume you've tested the fuse and the connection to the battery? Sounds like there's a bad connection somewhere. And having had a Bose sub in an RSX before, the amp is pretty cheaply made. I wouldn't rule out that it crapped out on you.

Also, you sent me down a rabbit hole looking at spare tire subs and I just discovered the Pioner TS-WX610A.

 

Thanks. Hmm, isn't weird that the shift beeper and the SUB both start and stop working at the same time together?

 

Well, I don't have a shift beeper in mine ... did you put that in yourself? I'd start looking at anything that didn't come with the car from the factory.