2017 imac 27" constantly crashing. AHCI disk queue manager error. What can I do to fix it?

If your iMac is constantly crashing and you're seeing an AHCI disk queue manager error, there are a few steps you can take to try and resolve the issue. Here are some troubleshooting suggestions:

• Ensure that your iMac is running the latest version of macOS. Sometimes, software bugs or compatibility issues can cause crashes. To check for updates, go to the Apple menu () in the top-left corner of your screen, select "System Settings/Preferences," and then choose "Software Update."
• Use Disk Utility to check the health of your hard drive and repair any potential disk errors. To do this, go to the "Applications" folder, then "Utilities," and launch "Disk Utility." Select your startup disk from the sidebar and click on "First Aid." Follow the instructions to run the disk repair process.
• If your iMac is Intel-based, Reset NVRAM/PRAM: Resetting the NVRAM (Non-Volatile Random Access Memory) or PRAM (Parameter Random Access Memory) can help resolve certain hardware-related issues. To reset NVRAM/PRAM, restart your iMac and immediately hold down the Command + Option + P + R keys until you hear the startup sound for the second time. Release the keys and see if the crashing issue persists.
• Booting your iMac in Safe Mode can help identify if the problem is caused by third-party software or drivers. To enter Safe Mode, restart your iMac and hold down the Shift key immediately after hearing the startup sound. If your iMac runs without crashing in Safe Mode, it suggests that a third-party software or driver might be the cause.

If the issue persists after trying the above steps, it may be necessary to contact Apple Support or visit an Apple Authorized Service Provider to diagnose and resolve the problem. They will have access to advanced diagnostics tools and can provide expert assistance.

Alternately, you can contact Apple Support directly by simply selecting the "Support" link in the lower left-hand side

of this forum's web page ... or go here: Get Support

It’s extremely highly likely that the HDD of your iMac is failing. You need a new OS disk. And reinstall. Specifically,

1. Try out and run DriveDx to verify the health of your HDD or the HDD portion of the Fusion Drive, if the iMac is configured so.
2. Fully back up using Time Machine. Then manually transfer user data as many as possible to an external disk, or a cloud service such as iCloud.
3. If the diag shows severe HDD errors, you need to prepare an OS reinstall. Run another full backup to Time Machine of the ‘downsized’ disk. Prepare a new external USB-C SSD, such as one from Samsung or LaCie, or 1T or greater.
4. This step is optional yet useful. Make a USB bootable OS installation media, such as a flash drive, of the OS you choose to reinstall. Test run it to make sure the media is usable. USB bootable media is a better way as it is more reliable than reinstalling through Recovery. And, it is always useful for OS maintenances or other reinstallations.
5. Now, run the installation media and install unto USB SSD. Run the new OS to see if you are satisfied with its performance and whether it’s issue-free.
6. Finally, you need to decide what to do with your internal disk. If it is only a HDD, you can still use it as a cold storage of large and non-essential files and backups. Typically these include redownloadable Music or Videos, Apps, or extra Time Machine backups of iOS and macOS at a given interval (monthly/quarterly). However, if you are using a Fusion Drive, you can split the SSD and HDD first using commands in Terminal. Note with the split all data on both disks will be erased and can’t be recovered. And, depend on the size of internal SSD and your use cases, you can set and use it meaningfully. You can even reinstall the OS on this internal SSD if it is 128G or larger. (And migrate the latest and the smaller Time Machine backup to it if the size fits). In this case, it is preferable to have an external SSD that can be used to hold some apps and live user data.
7. Installation, migration and setup are all straight forward and well documented. The most difficult part is how to config your system and understand where and what to install.

Hope this helps.

What a political correct answer. However, my ChatGPT says these is a 99.99% probability, based on statistical data of real human users and not tech writers, that the Hard Disk (McIntosh HD it is) should have failed or is failing.

And, statistically, HDD failure is the most common issues of iMacs up to model year 2019.

Finally, even an HDD fails or is failing, Disk Utility or Apple Hardware Tests or Apple Diagnostics tends to fail detecting such failure in many occasions, until the disk ultimately becomes unreadable or even unmountable.

And, after reinstallion the disk error persists and leads to system crashes, you need to dismount the HDD entirely. Terminal commands are available for this action. Or have the HDD replaced (with a Sata SSD). However, the iMac needs to be opened up for disk replacement, which is not easy to do.

None of the above is useful. OP can verify this.