If a certain diagnostic software isn’t present, your machine could be bricked.
Small repair shops and tech enthusiasts who attempt to fix their new Apple devices may be taking a serious risk in doing so. According to a report from The Verge, Apple confirmed that its new T2 security chip is designed to lock down devices after repair if it doesn’t recognize certain authorized replacement parts.

Read more: https://arstechnica.com/gadgets/2018/11/apples-t2-chip-will-block-some-third-party-repairs-of-new-devices/