Feedback coming from speakers!

I have a 2012 with the JBL system. The stock head unit died a couple of weeks ago and I replaced it with a Pioneer AVH 2330 nex. Years ago I installed focal 165s in another truck and swapped those out into the Tacoma’s front speakers, the rear speakers are currently stock but soon I’ll swap those out for focal 165as.

When I had the pioneer installed they kept everything wired through the factory amp which also kept the sub working. Since the install I have a slight hissing coming from the speakers when music is paused and the volume is at 0. I’ve been told that this is because the amp doesn’t have any adjustments. I’ve messed with the stereo settings but nothing fixes the hissing.

Is there a way to fix it?

 

Maybe check your ground?

 

Do you still get the hiss when you remove the inputs from the pioneer amp?