Diagnosis
The F1 error code indicates a problem with the oven's temperature sensor, which means it can't accurately read or regulate the internal heat.
How to Fix It
Unplug the oven and let it cool down completely for at least an hour. This is the most important step. Once it's cool, plug it back in. The error may clear on its own. If it does, try turning it on to a low temperature (like 200°F) without anything inside to see if it heats normally and the error stays away.
If That Didn't Work
The sensor probe (a thin metal rod) inside the top-right of the oven chamber might be damaged or have a loose connection. Unplug the oven, let it cool, and visually inspect the probe. If it's bent, corroded, or looks broken, it will need to be replaced. You can find the part online, but replacing it involves opening the top panel.
Heads Up
Don't ignore an F1 error and try to keep cooking. The oven could overheat significantly because it doesn't know the actual temperature, which is a safety risk. If the error persists after a cool-down, it's time to call Cuisinart support.