Running Apple Hardware Test and Apple Diagnostics on Mac: Guide

Introduction

Apple Hardware Test (AHT) and Apple Diagnostics are built-in tools for checking the hardware of your Mac. They help identify issues with RAM, processor, storage, graphics, and other components. In this guide, you'll learn how to run these tests on Macs with Intel and Apple Silicon processors, as well as how to interpret the results.

Requirements

Before you begin, make sure that:

• Your Mac is completely shut down (not in sleep mode).
• It is connected to a power source (charger for a laptop or power for a desktop).
• An internet connection (Wi-Fi or Ethernet) is required to download extended tests and diagnostics.
• For an Apple Silicon Mac without a built-in display (Mac Studio, Mac mini), an external monitor and keyboard are connected.
• It is recommended to back up your data using Time Machine, especially if the test reveals critical disk errors.

Step-by-Step Instructions

Step 1: Identify the Processor Type

First, determine which processor your Mac has to choose the correct launch method:

1. Click the Apple logo in the top-left corner of the screen.
2. Select "About This Mac".
3. In the window that opens, find the "Processor" line:
   • If it says "Intel Core..." — it's an Intel-based Mac (use AHT).
   • If it says "Apple M1", "M2", "M3", etc. — it's an Apple Silicon Mac (use Apple Diagnostics).

Step 2: Prepare Your Mac for the Test

1. Close all running applications.
2. Ensure your Mac is connected to a power outlet.
3. Connect your Mac to the internet (via Wi-Fi or Ethernet cable). This is especially important for:
   • Downloading extended tests on Intel Macs.
   • Running Apple Diagnostics on Apple Silicon (requires access to Apple servers).
4. If you have an Apple Silicon Mac without a built-in display (e.g., Mac Studio), connect an external monitor and keyboard.

Step 3: Run the Hardware Test or Diagnostics

The launch method depends on the processor type.

For Mac with Intel Processor (2013–2020)

1. Completely shut down your Mac: Apple menu → "Shut Down".
2. Press the power button to turn on your Mac.
3. Immediately press and hold the D key on your keyboard.
4. Release the key when you see on screen:
   • The Apple Hardware Test (AHT) interface with language selection, or
   • A loading progress (spinning globe).

Note: If the local AHT version is unavailable, hold Option + D to load the test via the internet (requires network connection).

For Mac with Apple Silicon Processor (M1, M2, M3 and newer)

1. Completely shut down your Mac.
2. Press and hold the power button (the power-on button) on the Mac's case.
3. Continue holding until the startup menu appears (a screen with several options, including booting macOS, Disk Utility, etc.).
4. Use the arrow keys or mouse to select "Apple Diagnostics" and press Enter (or click).
5. The Mac will automatically restart and begin diagnostics.

Step 4: Run the Test

After launching the test:

1. If a language selection appears, choose the desired language using the mouse or keys.
2. Select the test type:
   • Basic Test — a quick check of main components (5–10 minutes).
   • Extended Test — a thorough check of all components, including stress tests (can take up to several hours).
3. Click "Run" or "Continue".
4. Do not interrupt the process — this may lead to incorrect results or data corruption.
5. Wait for completion. Progress will be displayed on the screen.

Step 5: Check the Results

After the test completes, a result will appear:

• Successful: message "No issues found". The hardware is fine.
• Issues found: an error code will be displayed (e.g., PPD001, VDC001, 4HHD).
  • Write down this code (e.g., take a screenshot).
  • The error code indicates a specific component (power, display, memory, etc.).
  • To decode the code and for further actions, contact Apple Support or an authorized service center.

Checking the Result

You already checked the result in Step 5. However, if the test completed successfully but you continue to experience issues (e.g., random reboots, screen artifacts), the problem might be software-related, not hardware. In this case:

1. Update macOS to the latest version.
2. Reset NVRAM/PRAM and SMC (for Intel Macs).
3. Run Safe Mode to check for software conflicts.
4. Perform a macOS recovery/reinstall.

Possible Issues

Test does not start on Intel Mac

• Cause: Incorrect D key press.
• Solution: Ensure you press D immediately after powering on (before the Apple logo appears). Try an external keyboard if using the built-in one. Use Option + D to load via the internet.

"Apple Diagnostics" option missing on Apple Silicon

• Cause: Mac not fully shut down or power button not held long enough.
• Solution: Fully shut down the Mac (hold the power button for 10 seconds if unresponsive). Then hold the power button again until the startup menu appears (may take 5–10 seconds).

Test freezes or takes very long

• Cause: Extended test on a large disk or multi-core processor naturally takes a long time.
• Solution: Let the test finish. If the process is stuck on one stage for more than 2 hours, restart the Mac and run the test again, selecting the basic option.

Test load error (Intel Mac)

• Cause: Corrupted or missing AHT utility.
• Solution: Run the test via the internet (Option + D). If that doesn't help, reinstall macOS.

Error code is unclear

• Cause: AHT/Diagnostics error codes often point to a component but not a specific part.
• Solution: Note the code (e.g., 4MCD — memory issue, PPD001 — power issue) and contact Apple Support. Do not attempt to repair the hardware yourself.

Diagnostics pass but problems persist

• Cause: The issue may be software-related or only appear under load.
• Solution:
  1. Check system monitor activity (Applications → Utilities → Activity Monitor) for anomalies.
  2. Boot into Safe Mode (hold Shift during startup) and check if symptoms disappear.
  3. Perform a clean install of macOS.