I HAVE A PIONEER AVH-P5100DVD AFTER CONNECTING ALL

Check your ground and meter your power. If you don't have 12v or a solid ground, it's not going to turn on. You should have 3 power leads, one for ignition, one for constant, and one for illumination. Hope this helps. If you still have a problem, post a comment and I will help you troubleshoot it.

make sure u have connected the fm tunner silver box if not thats your problem if u do not connect it it wont power thats really important.

I had this exact same problem. The issue was the stereo was blowing the 7.5 radio fuse. I replaced it with a 10 and it works fine. hope this helps.

ok i just bought one the other day and had same problem ... what it is is i think the red acc wire the onr that has the black plastic thing on it cut the plastic thing off and reconnect wires and that should do it and you also need to plug in that metal box it comes with its kinda like a brain but you dont have to connect antenna up