Ground loop is happening. Here is some reading

http://www.crutchfield.com/S-wOkStfl...ech/kb350.html

or probably bad RCA's. Test them by swapping a new set across the seats to the amp for test purposes. If that solves it there is your problem.

if not try this procedure chart, because that hum is noise in the system. Follow chart till noise from subs goes away.

http://www.crutchfield.com/Learn/lea..._diagnose.html

 

Im not sure if this is the same thing but when I installed a full system in my friends car including a headunit speakers and an amp when we turned on the headunit, the speakers would pop. After speaking with crutchfield tech support(they are awesome btw) we were recommended a solution. Apparently the amp was turning on before the headunit and causing a pop. We were instructed to wire in line both a small resistor and capacitor. These were soldiered in line to the switched 12v going to the amp. Now I forget the specifics on the capacitor and resistor however what I can tell you is that it fixed our problem. I suggest getting in contact with someone from crutchfield tech support and see what they can do for you. Good luck and keep us posted.

 

make sure you amp turn on wire is connected to the blue/white wire from the pioneer harness, and/or turn down the frequency on the amp.

 

swapped RCA jacks on the back of the head unit. problem gone.

guess that set on the back I was using is FUBARED.