I have a broken digitizer and damaged LCD screen on an old iphone 3Gs. So I replaced them both with new ones. The problem is the new Digitizer/LCD assembly has a bad proximity sensor cable. The phone won't boot up past the apple screen when that #3 cable is connected, but it works fine when it's disconnected. This old phone isn't used as a phone. I was planning on giving it to my son to download some apps and use as an game console/ipod touch. Question: What does this cable do? And do I even need it????