So its probably just a bad connection on the back of the head unit. You can find wiring diagrams for the stock stuff here. I have no idea what you had to do to install the aftermarket unit.

 

ohh man I removed the head unit. cut the wires further back and rewired it one wire at a time. Still have power but no sound. Next step take the door panels off and look at the speakers? Seems like when I slammed the door or hit a bump it cut out and kick back in every now and then