I have an LG Optimus 4X HD and when I make a call, the screen goes black. It does not come back on when I move it from my face or when the call has ended. I cannot check call waiting, internet, contacts, call duration, use speaker phone or anything during a call. The only way I can end a call is by pushing the power/lock button. I have tried re-calibrating the proximity sensor thru the 'hidden menu', checked every possible solution under the settings and NOHING IS HELPING!! This is extremely annoying for me. Can someone please help me?? I am running on 4.1.2.
I have looked into how to disable the proximity sensor on the Galaxy S4 and Nexus 4.
The S4's instructions were on stackexchange: Screen turns off during call with Tecno F7
But it appears Android 4.x AOSP, by default, does not have a way to disable the proximity sensor (I would love to be proved wrong). That's the issue with the N4, and possibly with your 4X HD.
There is a third party application, which I have not tested, that claims to be able to do this: https://play.google.com/store/apps/details?id=com.itsme4ucz.screenoff