Using Internet Apple Hardware Test

One of the new features that appeared with Macs that shipped with Lion was Apple’s Internet Recovery. If you encounter a situation in which you cannot start from the Recovery HD, such as where the internal hard drive has failed or when you’ve installed a new disk without an OS on it, Mac models that were released after July 2011 can use Internet Recovery. Internet Recovery lets you start your Mac directly from Apple’s servers using a NetBoot-like process and gives you the same functionality as Recovery HD does.

Apple also made Apple Hardware Test (AHT) available in a similar fashion. Apple now ships most Macs with a hidden AHT partition, which allows you to hold down the D key at startup to boot your Mac using the AHT partition. From there, you can use the available tool to (hopefully) diagnose hardware problems on your Mac. However, if the AHT partition is not available and you have an internet connection, you can use Internet Apple Hardware Test. See below the jump for the details.

Update – May 26: The AHT partition is actually mounted from a disk image stored in the factory-supplied Recovery HD partition. If the factory-supplied Recovery HD partition is removed, or replaced by another Recovery HD (either by using the Mac App Store’s Lion installer or by other means), the AHT disk image is gone and there is no way I’m aware of to bring it back or rebuild it.