Why does autocorrect change 'I' to 'o' and 'U' on iPhone?

If you go to Settings > General > Keyboard > Text Replacements, do those words show up there? You may have text replacements setup which would change those words accordingly.

If that doesn't work, go to Settings > General > Transfer or Reset iPhone > Reset > Reset Keyboard Layout. This will reset the keyboard dictionary and any custom layouts/keyboards you may have.

swamz97 wrote:

Thank u. It didn’t work bro

Perhaps you are mistyping them? I, O, and U are all next to each other on the iPhone's keyboard. The advice I suggested would have fixed it unless there is a bug in iOS, which is unlikely as the forum would be flooded by now.