Why is my iPhone showing an “Important Message” or “Unknown Part” warning from Apple?

What do these messages mean?

Fear not! These messages appear when repair work has been done to your device to give information on the replaced component: battery, screen, camera (depending on your iPhone model, see below). Only an Apple Genius Bar or an Apple Authorized Service Provider can replace a component in the latest iPhones without prompting this message, but this doesn't mean that your battery has an issue or is defective — it only means it was replaced with a new battery (or camera or screen) that works just as efficiently as the original one.

These messages don't affect your device’s performance in any way. This message will be visible on the lock screen for 4 days and then for 15 more days in Settings. Getting this message doesn't impact the iPhone's performance. Even if the part replaced by Apple you get message as "Genuine Part".

iOS 18 and Repair Assistant:

Apple introduction of the Repair Assistant in iOS 18 aims to streamline the repair process by integrating software diagnostics with hardware replacements. However, the changes aren’t as straightforward as one might hope, especially for repairs using third-party parts. This new feature brings both positive and challenging implications depending on the type of battery used.

OEM Pulled Battery: Similar Results with Health Reflecting Usage

An OEM pulled battery replacement produces results similar to a new OEM battery. The Repair Assistant successfully pairs the battery, screens or other Oem parts and the device shows a service history entry. However, the battery health reflects the actual condition of the used battery, instead of 100%. This is expected, as the health is dependent on its previous usage, but otherwise, the battery integrates perfectly with iOS 18.

REPART Battery Cell with BMS Board Swap: No Unknown Part Message, 100% Battery Health

iOS 18: Progress Made, Yet Third-Party Battery Restrictions Remain

iOS 18 has loosened the restrictions on independent repairs. OEM new and pulled batteries paired well with Repair Assistant, showing service history and battery health. However, third-party batteries, screens, camera including third party  parts, are still flagged as Unknown Parts with no battery health displayed.