Apple has implemented a protection system in iMac Pro and MacBook Pro that requires a proprietary diagnostic utility to repair some of the components. The function is responsible for the Apple T2 chip with the Secure Enclave coprocessor, which is also responsible for encrypting information.
More precisely, a third-party organization will be able to carry out repairs, but it will not be able to complete it – the computer will not function. For MacBook Pro 2018, it’s about the display, motherboard, Touch ID module, keyboard, battery, trackpad and speakers. For iMac Pro – the motherboard and storage devices.
If these elements are repaired without the subsequent launch of a special utility, the system will not work. This software is available only to Apple store professionals and authorized services.