Apple has just released a revised version of the iOS 9.2.1 software update, which essentially fixes the Error 53 issue. Last month when Apple released the software update, many users reported that it bricked their iPhones. Later it was revealed that Apple has added a ‘security’ feature to iOS that bricks an iPhone or prevents it from booting properly if its Home button’s Touch ID sensor has been repaired improperly or by a third-party repair service. While Apple has not actually released a new iOS update to fix this issue, it has revised iOS 9.2.1 that now carries a build number of 13D20 instead of 13D15.
If you are already running iOS 9.2.1 and don’t have the Error 53 issue, then you won’t receive any new OTA updates. However those users whose devices got bricked after the update can download the new build from iTunes or an IPSW (links given below) and restore their iPhone. Upon restore their iPhone will be able to boot without any problems.
Below you can find the iOS 9.2.1 13D20 IPSW for iPhone 6s, iPhone 6s Plus, iPhone 6 and iPhone 6 Plus.
In addition to fixing the problem in a revised build of iOS 9.2.1, Apple has also issued an apologizing statement to TechCrunch.
Some customers’ devices are showing ‘Connect to iTunes’ after attempting an iOS update or a restore from iTunes on a Mac or PC. This reports as an Error 53 in iTunes and appears when a device fails a security test. This test was designed to check whether Touch ID works properly before the device leaves the factory.
Today, Apple released a software update that allows customers who have encountered this error message to successfully restore their device using iTunes on a Mac or PC.
We apologize for any inconvenience, this was designed to be a factory test and was not intended to affect customers. Customers who paid for an out-of-warranty replacement of their device based on this issue should contact AppleCare about a reimbursement.
So there you go, if you were experiencing the Error 53 after restoring your iPhone, then simply download the latest iOS 9.2.1 from iTunes and restore your device. Afterwards you can restore the backup as usual. (Apple)