This actually just happened to me. I had my phone carrier send me a new phone and the actual day that the phone came I fixed my current iPhone 6 Plus from the error 53 problem. I had spent 8+ hours trying to fix this problem and couldn't find any solutions to it that did not involve opening the actual phone reconnecting pieces or changing pieces. So I kept reading online that people were uninstall and reinstall and iTunes but nobody actually confirm that this actually work. As a last resort when the day came before it actually arrived I try this method sure enough lo and behold after I got back from playing video game with my friend for a couple hours my phone was fixed I couldn't believe it. I'm actually typing this right now on the phone that have the nerve 53 message my phone was correct don't get me wrong there was absolutely nothing I could do it was a useless piece of junk but now it's been revived. It's a daunting task I know but just try that method at least give it one try. Work for me after all....