Happened to me the same problem, what I did was to inspect well near the connectors and set me well that a connector had broken and what I did was I made a bridge with a silver writer. and it worked but I had to connect a new screen for it to work and then place the iphone screen.
And iphone is working properly
Fixed with Silver Writer
i use a Macro Lens for iphone 5
Link Silver Writer
never use it direct the writer, put some on a sheet with something that has the fine point you can do it without touching other connectors or you can make a short circuit.