Troubleshooting a Non-Responsive Mac: Initial Steps and Beyond

Posted: October 4, 2023

Initial Troubleshooting Suggestions

When you encounter the issue "Unable to write to the last block of the device," the first step to resolving it is applying some initial troubleshooting methods. These suggestions are straightforward and don't require any advanced technical skills. They primarily focus on checking the connection cables and the Disk Utility tool. Here are the initial steps to consider:

Try Replacing Cables for External Drives

If the device you're having issues with is an external drive, the simplest first step is to replace the cables. Sometimes, faulty cables can lead to communication issues, which might cause errors when writing to the disk. This communication error can result in the inability to write to the last block.

Attempt to Erase the Disk Drive via Disk Utility Multiple Times

For Mac users, Disk Utility is a common method to erase a disk drive. However, on occasion, Disk Utility might not successfully wipe the drive completely on the first attempt. It can also cause the "Unable to write to the last block of the device" error. Therefore, it's suggested to try erasing your disk drive through Disk Utility multiple times, as this can potentially resolve the issue.

Swap the SATA Cable or Controller

Sometimes, a bad SATA cable or controller can cause connection issues, leading to a writing error. Swapping out your SATA Cable or Controller for a working one may solve your problem. It is a sensible next step once the basic cable checks have been performed.

Test the SSD via an External Enclosure

Another step to determine the cause of the issue is to remove the SSD from your Mac and test it with an external enclosure. If your SSD can be successfully erased when connected externally, then the error might be due to a faulty hard drive cable or controller, which would need to be replaced.

Attempting to Use Internet Recovery

If initial troubleshooting has failed, you can consider using Internet Recovery Mode on your Mac. The process involves accessing recovery tools directly from Apple's server, allowing you to install the latest compatible macOS version for your Mac. This option, however, is only applicable for Macs based on Intel processors and will not work on M1 and M2 Macs. Here's how to erase the internal hard drive using Internet Recovery:

Power Down Your Mac

The first step in Internet Recovery Mode is completely powering down your Mac. It's important to shut down your system completely to ensure a proper reboot in the Internet Recovery Mode.

Enter Internet Recovery Mode by Holding Option + Command + R

After turning off your Mac, press the power button and simultaneously hold down the Option + Command + R keys. You should continue holding these keys down until you see a spinning globe appear on your screen. It indicates that your Mac is now in Internet Recovery Mode.

Select Disk Utility

Once in Internet Recovery Mode, look for the macOS Utilities section and select Disk Utility. Then click on Continue. You'll be presented with selecting "View," followed by "Show All Devices."

Erase the Startup Disk

Identifying your startup disk is the next step, typically at the top of the 'Internal' section. With your startup disk selected, click on 'Erase.'

Pick a Name and Format for the Startup Disk

After selecting 'Erase,' you will have to provide a name for your startup disk. If your macOS version is 10.13 or higher, configure the format as APFS and set the scheme as GUID Partition Map.

Attempt to Erase Once More

After configuring your disk, click 'Erase' again to begin the process. If, after all these steps, you still encounter the "Unable to write to the last block of the device" error on your Mac, it would suggest that you proceed to the next solution.

Using a Bootable Installer

If the "Unable to write to the last block of the device" error persists even after trying the above methods, you can consider using a bootable installer. This method involves using Disk Utility after loading from a bootable installer, bypassing any potential internal issues. Here are the steps:

Create a Bootable USB Installer

Start by creating a bootable USB installer, which is crucial for this method. Also, ensure that the USB Flash Drive or device you're using to create the bootable installer has at least 14GB of free storage.

Connect the Installer to the Mac and Ensure an Internet Connection

Once the bootable installer is ready, connect it to your Mac. Ensure your Mac is connected to the Internet, as some operations during this process might require online services.

Boot from the Installer

Power off your Mac, then unplug all external devices, leaving only the power cord and the bootable installer connected. To boot from the installer, follow these procedures:

For Intel Macs:

Power on your Mac, and then immediately press and hold the Option key until you see the bootable volumes.
Select the bootable installer and click on the up arrow to proceed.

For Apple Silicon Macs:

Press and hold the Power button until you see the bootable volumes.
Select your installer and click on Continue to proceed.

Choose Disk Utility in the Installer

Once your Mac boots from the installer, select Disk Utility and click Continue.

Follow Instructions Similar to the Method in the Previous Section

After choosing Disk Utility, follow the instructions to erase the startup disk described in the Internet Recovery Method. Further technical assistance may be required if this process doesn't rectify the "Unable to write to the last block of the device" error.

Final Considerations and Troubleshooting Steps

If the error "Unable to write to the last block of the device" persists even after trying all methods, there are other considerations that you can take into account. It could be that the drive is defective, and further technical assistance may be required. Below are final considerations to keep in mind:

Consider Replacing the Drive

Occasionally, the error may indicate that your drive is defective. In such a case, no amount of troubleshooting will rectify the issue, and the best course of action might be to replace the drive. It can particularly be true if the machine fails to recognize the drive. Be sure to consult with a technical expert before making this decision.

Consult with Apple Support

If the error persists and all the troubleshooting methods have failed, it's advisable to seek help from Apple Support. Technicians should have more advanced methods to diagnose and possibly fix the error. Contacting Apple Support should be easy through the website, over the phone, or by visiting a physical Apple store.

Maintain Regular Back-ups to Prevent Data Loss

Lastly, with the understanding that such errors can occur, it's prudent to regularly back up your data to avoid permanent data loss. Time Machine or other back-up services can help ensure that all your files are safe, allowing for an easy restore should your drive become unresponsive or fail. An external hard drive can be an excellent source of backup data.