Originally Posted by Musclefan21
That is true. I have been trying to figure this one out for a while now and i am going nuts. they did wired everythng though. there are foreign wires behind the head unit and similar wires when i pulled the pass. side door speaker. the guy simply replaced the whole sound system very poorly. I already spent too much on this crap and i bet you it will cost me 2x times more to get it to normal level.
The "Foreign" wires behind the dash are probably for the Nav. The '04 was never equiped with the nav, BUT the wires are there and it is very easy to install in the '04 compaired to the '05 and on models. I am thinking the factory amp might have a problem with the output for that speaker. Test and compare it to the other speaker output. It is worth a try