Ok so i was going to install an aftermarket hu on my 2001 accord and so i took out the factory one then i bought the wireing harness because i couldnt figure out the wire colors and after that i connected everything properly but it still wont turn on? so then i returned everything like it was from factory with everything like it was to see if it was the aftermarket hu but it still didnt turn on. Is this normal or is there like a code in the cars computer that disables the stereo power after the factory one is removed? how do i fix it?

Not sure about a code but I would double check the constant and ignition 12v. sources.

check to make sure you didn't blow a fuse. if you deck is similar to mine, it will say CODE right on it if it's needed. Make sure again that all wires are connected firmly to include your antenna.

I would guess blown fuse too .... the factory stuff is just plugging in a harness, kinda hard to screw that up.