Failed startup

Created at: 2021-04-29 02:58:52
Questioner General

My laptop cannot start, it shows a message that there is an error and the Mac OS can't be started, please any advice! It shows the following messages

Answer #1:

By: Isaiah Grimes

My laptop cannot start, it shows a message that there is an error and the Mac OS can't be started, please any advice! It shows the following messages

Answer #2:

By: Katarina Carroll

Also this message is shown

Answer #3:

By: Icie Lakin

The first one is..

• error code -3403D simply means your computer won't run the internet-based AHT or the Command+D one because it's too old. 

Apple Hardware Test (AHT)


Apple computers ship with a pre-installed suite of hardware diagnostic tools, known as Apple Hardware Test (AHT). In principle you can start them by holding the d key while booting. Newer models support holding option d to load AHT over the internet. Refer to the official Apple documentation for details: Using AHT on Intel-based MacsMountain LionMavericks and Yosemite. Apple redesigned the AHT, now called Apple Diagnostics, for Macs introduced after June 2013. Consult the reference codes to interpret the results.

If however, you reinstalled an older computer from scratch, the diagnostic tools might no longer be available. Unless you have the original disks that came with your computer, there seems to be no way to restore the AHT.

It happens that Apple provides disk images with AHT for most computers, but does not make the links publicly available. Various blogs and forums, mostly Riven by Five and have gathered a list of download links. The rest were obtained by scraping for all the links of the form 0(18|22)-\d{4}-A.dmg.

Even though there's no guarantee that this list is correct or complete, some links can come in very handy to whoever is trying to debug hardware problems.

You can use the following terminal commands to determine the model and board ID of your computer:

sysctl hw.model | awk '{ print $2 }'

ioreg -l | awk -F\" '/board-id/ { print $4 }'

Download the AHT for your computer model and use the contents to restore the /System/Library/CoreServices/.diagnostics folder, then reboot while holding d to start the diagnostic tools. Alternatively you may try with a bootable USB stick, as described below. This is also the preferred way on OS X 10.11 or later, where the System Integrity Protection (SIP) no longer allows writing to system folders.

When trying to open an old dmg you may get the error 'legacy image should be converted'. To convert it to a newer format, open Disk Utility, in the menu Images click on Convert and select the dmg to convert and save it under a new name.

Note that there is no one-to-one correspondence between hardware model and AHT. For some models no hardware test could be found, while others seem to have multiple AHT. As the differences are not clear, feel free to try them out, to see which one works best for your hardware.

1. Start up from macOS Recovery

To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following combinations on your keyboard. Command-R is generally recommended, especially if you never installed macOS Sierra 10.12.4 or later…

Command (⌘)-R

Install the latest macOS that was installed on your Mac.


Upgrade to the latest macOS compatible with your Mac.


Install the macOS that came with your Mac, or the closest version still available.

2. Decide whether to erase (format) your disk

If you need to erase your disk before installing macOS, select Disk Utility from the Utilities window, then click Continue. You probably don't need to erase, unless you're selling or giving away your Mac or have an issue that requires you to erase. Learn more about when and how to erase.

3. Install macOS

After starting up from macOS Recovery, follow these steps to install macOS:

  1. Choose Reinstall macOS (or Reinstall OS X) from the Utilities window.
  2. Click Continue, then follow the onscreen instructions to choose your disk and begin installation.
  3. If the installer asks to unlock your disk, enter the password you use to log in to your Mac. If it doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk

  1. Please allow installation to complete without putting your Mac to sleep or closing its lid. During installation, your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.

If your Mac restarts to a setup assistant, but you're selling or giving it away, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.

If you never installed macOS Sierra 10.12.4

If macOS Sierra 10.12.4 or later was never installed on your Mac, macOS Recovery works differently:

  • Command-R is still the recommended way to start up from macOS Recovery. This combination makes sure that the installation isn't associated with your Apple ID, which is important if you're selling or giving away your Mac.
  • Option-Command-R installs the macOS that came with your Mac, or the closest version still available.
  • Shift-Option-Command-R isn't available.