Using Apple Hardware Test
Apple Hardware Test (AHT) contains a suite of diagnostics that will test the hardware of your computer. It's a great way to rule out a hardware issue when troubleshooting your computer.
Before you begin
- Important: If your Mac was released after June 2013, you will use Apple Diagnostics rather than Apple Hardware Test (AHT). See Using Apple Diagnostics for instructions.
- Consider doing some preliminary troubleshooting to determine if your issue is related to hardware. You can try to determine if the cause of your issue is related to hardware or software by following Isolating issues in Mac OS X. AHT can help determine which hardware component may be causing the issue.
- Before starting AHT, be sure to disconnect all external devices except the keyboard, mouse, display, and Ethernet adapter. Also disconnect any external optical drives.
- If you are testing a Mac notebook, perform the following additional steps:
- To prevent your computer from shutting down during testing, connect the correct wattage AC power adapter to an AC power outlet.
- Set up your computer on a hard, flat, stable work surface that allows for adequate air circulation under and around the computer (such as a desk, table, or counter).
Note: Your test results will appear in the window in the bottom-right of the console.
- Press the power button to turn on your computer.
- Press and hold the D key before the gray startup screen appears.
- It takes a minute or so for AHT to start up and inspect your hardware configuration. While this is taking place, an icon appears on the screen:
- When the process is complete, select your language and click the right arrow. If you aren't using a mouse, you can use the up and down arrows to select a language and then press the Return key.
- The AHT console appears. You can choose which sort of test or tests to perform:
- To perform all of the basic tests, click the Test button or press the "T" key or the Return key.
- To perform a more thorough diagnostic test, select the "Perform extended testing" checkbox under the Test button before you click the Test button.
- To exit AHT, click Restart or Shut Down at the bottom of the window.
Some Macintosh computers that shipped with OS X Lion and later support the use of Apple Hardware Test over the Internet. These computers will start up to an Internet-based version of AHT if the hard drive does not contain AHT. An Internet-enabled connection via Ethernet or Wi-Fi is required to use this feature. Internet-based AHT functions the same as AHT on the hard drive or flash storage outlined above.
The Mac NoteBook and Desktop computers listed in Computers that can be upgraded to use OS X Internet Recovery will require a firmware in order to support the Internet version of AHT. Without this update you may see the behavior discussed in this article.
Using Apple Hardware Test on computers with OS X 10.5.5 to 10.6.8
AHT is located on the Applications Install Disc 2 and should be included with your computer or the MacBook Air Software Reinstall Drive on a MacBook Air (Late 2010). To start AHT on these computers make sure the Applications Install Disc 2 is inserted into the built-in optical drive, external Apple Superdrive, or for the MacBook Air (Late 2010) be sure the MacBook Air Software Reinstall Drive is inserted into a USB port. Please then follow steps 1-6 outlined in the "Using Apple Hardware Test on computers with OS X 10.7 or later" section of this article.
Using Apple Hardware Test on computers with OS X 10.5.4 or earlier
AHT is located on the Mac OS X Install Disc 1 and should be included with your computer. To start AHT on these computers make sure the Mac OS X Install Disc 1 is inserted into the built-in optical drive or external Apple Superdrive. Please then follow steps 1-6 outlined in the "Using Apple Hardware test on computers with OS X 10.7 or later" section of this article.
To run Apple Hardware Test remotely from another computer to a MacBook Air (Original), MacBook Air (Late 2008), or MacBook Air (Mid 2009):
- Make sure to install Remote Install Mac OS X on the other computer.
- Insert the Mac OS X Disc into the optical disc drive of the other computer.
- For Intel-based Apple computers shipping with Mac OS X v10.5.4 or earlier,AHT is located on the Mac OS X Install Disc 1 and should be included with your computer.
- For Intel-based Apple computers shipping with Mac OS X v10.5.5 or later, AHT is located on the Applications Install Disc 2 and should be included with your computer.
- If your other computer is a Mac, open /Applications/Utilities/Remote Install Mac OS X. On Windows, choose "Remote Install Mac OS X" from the Install Assistant.
- Read the introduction and hold down the Option key while you click Continue in Remote Install Mac OS X to launch AHT.
- On your MacBook Air, when the AHT chooser screen appears, select the language for your location.
- Press the Return key or click the right arrow button.
- When the AHT main screen appears (after about 45 seconds), follow the onscreen instructions.
If AHT detects an issue, it displays an error code. Make a note of the error code before pursuing support options. If AHT doesn’t detect a hardware issue, the issue may be software related.
- On the other computer, click Quit to exit Remote Install Mac OS X. If you see a message saying the MacBook Air will be disconnected, click Quit Anyway.
The Hardware Profile tab of AHT provides specific information about your computer. To see this information, click the tab, then select a subject area on the left.
You may also use the following resources for assistance identifying your Mac NoteBook or Desktop: