Nexus 4 screen regularly blacks out when make a call

Its not actually a fault, its so your phone doesn't start ending your call or changing things when its pressed up against your face, as this activates the touch screen similar to when your fingers move across the screen. If you remove it from your face and wait a few seconds at most it will switch the screen on again and you can end your call.

You CAN make it so that lock button ends your call in settings, have a look under settings for how to do this or do a quick Google search :)

the problem is associated with the proximity sensor. in order to fix it just remove the screen protector from that region. mind you it is not a software or hardware problem. its just the type of proximity sensor in the nexus 4. due to this you are advised to use thin screen protectors or just avoiding the sensor area.

trust me it works.

Do you use a display foil? If yes, check if the foil covers the distance sensor in the upper left of the phone.

I have had the same problem also since replacing the screen.

I am not certain but i think the problem might be a screen protector on the inside sensor porthole - one which needs to be peeled off before installation. I tried doing this before fitting the new screen but couldn't just peel it off. I ended up sort of scratching it off badly with some bits left behind.

Either way it still didn't work for me but if what people say about screen protectors is anything to go by this could be an issue.

The remedy is a weird one.

You must remove the logic board. When you do this you will see the proximity sensor on it has a black rubber covering with two holes. One big and one small.

Take the rubber covering off and flip it.

I'm not sure why it works, but I've used this to fix this problem dozens of times