Pioneer DEH-P3900MP CD Player "car subwoofer humming powered" Questions

ground just disconnect move to better ground check the amp ground the same way as decribed above if you have this humming sound, try to ground the rca to your car body ground. that will do the trick..

...subwoofer ouput rca's? if so you can control the level and frequency of the sub on the face in the audio menu. if this is not the issue try new rca cables. you can run them outside the car first just ...