So i did some searching here and on other sites and can't find a culprit other then maybe the head unit.
Here is the deal:
I have a 2003 - I've have issues with my rear defogger not working and my CD player never worked, so i went to the wrecker a couple days ago and saw a 2004 with the head unit still intact.
So i bought the stereo, hvac controls and the bose amp.

Swapped the stereo and hvac over, defogger still not working, but the cd player works! yay...then today i noticed the sub doesn't work.
So i figured i'd swap the factory amp, well low and behold the amp and connectors are different - 03 is a black amp, 04 is a silver (actually there was a tag on it saying it was from a 2005, from another wrecker maybe)

So i'm wondering if the stereos from 2003 -2004 changed enough that the output from the headunit to the amp isn't running the sub wires?

I'm hoping someone can shed some light on this, i would like to keep the unit in since the cd player works.

thanks!

 

Update:
Put the old unit in and sub still didn't work. Went to the back and gave the amp several good wacks, and it ended up turning on. So i'll keep my eyes out for another black single harness amp.
However, i did notice that the new unit when on CD mode the left side speakers cut out. Did some searching and this appears to be a common problem - sadly another issue to deal with...
Someone did say the issue is a loose ribbon harness internally, so i might open the unit up and take a look around.

I might just give up and install an after market unit, but i really do hate the metra look and the JDM is too pricey.

 

Aftermarket is the way to go!!

 

If it's the same amp as the 06 coupe I'd send it if you cover shipping. Been sitting in my closet for years