Due to advanced security features of the Apple T2 chip, iMac Pro and 2018 MacBook Pro models must pass Apple diagnostics for certain repairs to be completed, according to an internal document from Apple obtained by MacRumors.

For the 2018 MacBook Pro, the requirement applies to repairs involving the display, logic board, Touch ID, and top case, which includes the keyboard, battery, trackpad, and speakers, according to the document. For the iMac Pro, the requirement only applies to logic board and flash storage repairs.

If any of these parts are repaired in an iMac Pro or 2018 MacBook Pro, and the Apple diagnostics are not run, this will result in an inoperative system and an incomplete repair, according to Apple's directive to service providers.

Apple's diagnostic suite is limited to internal use by Apple Stores and Apple Authorized Service Providers, as part of what is called the Apple Service Toolkit. As a result, independent repair shops without Apple certification may be unable to repair certain parts on the iMac Pro and 2018 MacBook Pro.

Moreover, when the iMac Pro and 2018 MacBook Pro are eventually classified as vintage products, meaning they are no longer eligible for hardware service from Apple, repairs through alternative channels might not be possible.

MacRumors has reached out to Apple for comment.

This requirement is a result of the T2 chip, which integrates several previously separate components, including the system management controller, image signal processor, audio controller, and SSD controller. It also features a Secure Enclave coprocessor for secure boot, encrypted storage, and authenticating Touch ID.

To initiate a Mac repair, visit the Get Support page on Apple.com.

Update: Despite the specific wording of Apple's document, which says failure to run Apple diagnostics after certain parts are replaced in T2-equipped Macs "will result in an inoperative system," the repair experts at iFixit swapped out the display and logic board on a 2018 MacBook Pro, and it remained operational without passing diagnostics.

iFixit is not an Apple Authorized Service Provider, so at this time, it appears that independent repair shops should be able to repair the iMac Pro and 2018 MacBook Pro without issue. It's unclear why Apple's document suggests otherwise.