I have heard quite a few car stereo shops tell me that Pioneer H/U's are notorious for having ground loop and alternator whine issues once they are connected to an amp. I've redone my wiring twice now and I still get ground noise and alternator whine. Anyone with Pioneer H/U's having this same problem?

 

I copied this from another forum, I can't personally confirm it's accuracy but have heard something similar to it many many times......

Pioneer headunits have a 'fuse' on the main ground circuit of the pc board.They are extremely sensitive to spikes(like when the RCA's are being plugged in with the radio turned out).It causes the earth to go open circuit and you then pick up all sorts of noise.Get the unit to a technician and get him to bypass that lil fuse and you wont have the problem again

 

The scion cars are not well shielded against noise but what is being suggested about having the radio looked at by a technician might be good advice. I always run Alpine equipment and don't have that type of issue. Post up what corrects that problem once you get it sorted out.