Apple changed its mind about Error 53 being a security feature and allows a phone with a modified Touch ID sensor to function with the Touch ID feature disabled. Disabling phones from restarting, simply because they were repaired at an unapproved shop did not sit well with people. The public backlashed and Apple did what it needed for customers to be happy. Apple apologized and released a patch to iOS 9.2.1 that will disable the bricking feature that Error 53 was causing. When an unauthorized modification is made to the Touch ID sensor, perhaps when replacing a faulty home button, the iPhone threw an error and would not restart. Then when plugged into iTunes to recover the software, you were led through the restore process and the phone would never completely restore. With the new patch, iTunes will allow the device to restore and function normally, the downside is the modified Touch ID will not be active and become useless. The guys over at iFixIt.org have followed Apple's official guidelines and were able to successfully follow new prompts to restore iPhones that have a modified Touch ID sensor. Source | Via | Via...
Source: http://www.gsmarena.com/apple_fixed_its_error_53_modified_touch_id_sensor_wont_brick_iphone-news-16717.php
