Why does my iPhone 11 keep shutting down saying CPU 0 caller?

That “CPU 0 caller” message is part of a system panic log—it usually means your iPhone is crashing at a low level, possibly due to hardware instability or a serious iOS bug. If it keeps happening, it could be related to:

• Overheating (especially if it shuts down during heavy use or charging)
• Battery or logic board issues
• A corrupt iOS install or app that's messing with system processes

Here’s what I’d try:

Back up your iPhone, then do a full restore via a computer using Finder (Mac) or iTunes (Windows). Set it up as new (at least temporarily) to rule out software.

If it still crashes after that, you’re likely dealing with a hardware issue. In that case, it’s time to visit Apple Support or a Genius Bar for a diagnostic.

Unfortunately, iOS doesn’t give a user-friendly explanation for crashes like this, so “CPU 0 caller” is just Apple-speak for “something went very wrong.”

If possible provide a screenshot of where you are seeing this and/or apps you are using when this happens. If you happen to be using 3uTools, then that is your problem and you will need to factory reset your device.

Perhaps “CPU” refers to one of these organizations (from Wikipedia):