This guide solve my problem.
I noticed about the problem when flashed AOSP based Rom. So, thinked it was a rom bug.
Then, flashed stock again and find the issue was still there.
After trying whit compressed air, and nothing changes, rooted my phone (again) and follow this guide, and proximity sensor is working again.
I am glad it worked for you. I have heard that this is a huge issue for the S4. Not sure about other models.
But the point of my post (and I have the Verizon edition BTW) is to say THANK YOU! I got to the point where every time I made a phone call I knew almost certainly my screen wouldn't turn on and even half the time hitting the home button wouldn't do the trick. I know the issue is my otter box defender series, which never caused this problem until about a month or two ago. But I need the otter box and this fixed my problem... Thank you thank you! No more random voice mails from me because my screen won't turn on haha
Edit: For those on AOSP, if you type the value in the calculator, swipe left and hit HEX, it will give you the hexadecimal value you need
Ever since I flashed any custom ROM on my tmo S4, the proximity sensor hasn't worked right. Screen would never wake after a call ended, even the app I use to keep the screen off in my pocket (Gravity Screen, pretty cool app) wasn't working. I used the little app referenced in the OP, and it all works again! Thanks!
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