Vertical line on iMac Pro 5K screen

There are few user fixes for serious display defects, and diagnosing video defects remotely—like here— is even more of a challenge.

You can try :

— a restart.

— if no joy, a Safe Mode Boot

Is the image you posted a screenshot or one taken with a separate camera, like a phone camera? If the latter, take a screenshot.

If the line shows in the screenshot, you have a video hardware issue that would require a new logic board to fix. If it does NOT show in the screenshot, that points to an issue within the display assembly.

Otherwise, what remains is having Apple evaluate. Check this suport page:

https://support.apple.com/en-us/102772

to see if iMac Pros are still being serviced by Apple. I have one source that says they are still supported but it is not an official Apple source.

If it is down the center of the display.

Then it could be a remnant of the Split Screen feature.

see > Use apps in Split View on Mac

If not, then the fault is with the iMac Pro's display.

In that case, the fix is to find someone that can replace the display.

see > Find Service Locations

Or replace the 8~9 year old iMac Pro, with a new iMac or Mac mini and 27" display.

see > Help Me Choose a new Mac

Thank you for sharing your concerns. 😉

First, let’s see if this issue happens in Safe Mode:

1. Shut down your Mac.
2. Press and hold the power button on your Mac. As you continue to hold the power button, your Mac turns on and loads startup options. When you see Options, release the power button.
3. Select your startup disk. It's named Macintosh HD, unless you changed its name.
4. Press and hold the Shift key, then click the “Continue in Safe Mode” button below your startup disk.
5. Log in to your Mac. You might be asked to log in again.

If the strange behaviors do not occur, then it may possibly be a software issue.

If the issue doesn't continue in safe mode:

Leave safe mode by restarting your Mac normally, then try to reproduce the issue.

If the issue doesn't return, it might have been resolved by the other things that safe mode did at startup, such as checking your disk and clearing caches.

If the problem persists, then let’s try this:

• Software Update.
• Use Apple Diagnostics to test your Mac.

If none of those ideas work, then I recommend service.

Service Checklist:

• Mac service pricing.
• Check AppleCare Coverage.
• Get your Mac ready for service.

Click ▶︎ Start a Service Request. ⚛️

Need more help?

• United States: 1-800-APLCARE.
• Contact Support.
• Mac Support.
• Mac User Guide.

Click ▶︎ Check Repair Status. 🔧

Good luck! 👋🏼😉

Smiliñ 😎 Brian