During idle and acceleration I can hear a high pitched engine noise
from the speakers. Actually it seems to be only coming from the rear
speakers in my car but not the sub. As I accelerate the noise gets
louder and higher pitched.

When I turn the radio off or put the volume down to zero it goes away
completely. Also it happened suddenly while driving down the road.
Once second fine, next WHINEEEEE

I have a Pioneer DEH-P4700MP installed in my Scion tC. I also have a
sub installed in the trunk.

Has anyone ever heard of something like this before?

 

i used to have it, untill i read this.....
https://www.scionlife.com/forums/vie...ight=ten+audio

 

its called the alternator whine, more than likley you have a bad ground. Make sure you sand down the ground good with no paint left, I re-did my grounds and it worked!

 

If that doesn't work or you don't feel like dealing with all of that, get a ground loop isolator or two. If you are using a 4-channel amp, then you will need 2 ground loop isolators. Throw em on between the amp and the receiver and it should solve the problem. But if you would prefer to attack it from the source rather than adding a piece to eliminate it, then redo your grounds and make sure you have nothing interfering with something else. I used ground loop isolators for a while until I found out that it was the satellite radio. There is no way to ground that, so I threw a ground loop isolator on that one piece rather than on the whole system and it took care of it.

If the ground loop isolators between the amp and the head unit didn't work, then the problem is elsewhere. You can get em at www.crutchfield.com

 

I actually just re-did all the wiring on my sound system. I had a custom system and sold it and put in a 2 channel amp for the speakers. I only have 2 speakers working! lol

But I had the same problem, that "whining" noise. I had a bad ground it fixed it. Try to make your ground as short as possible.

 

Thanks guys, I bet it has to be a ground.

Makes sense too since it happened so suddenly.

 

also make sure your signal wires and power wires are not ran together down the car, if they are run down seporate sides but some are lose back by the amp make sure they did not get moved around during driving and are now laying back there running parallel sp?