FiveHundred automatic temperature control failure

Sounds like a classic case of a faulty interior temperature sensor. The error memory pretty much confirms it. When those go bad, the whole climate control system can go haywire. Have you tried checking the sensor's connections? Sometimes it's just a loose plug or a damaged wire. Where is the sensor located in your car? I would be happy to look it up for you.

I haven't checked the connections yet, honestly. I'm not even sure where to find the interior temperature sensor on this model. Any hints?

Okay, so I checked it out. It's usually behind the small grille on the dash, near the steering wheel. It's worth a look, but with those symptoms and the error code, it's probably the sensor itself. I'd recommend taking it to a workshop. They can diagnose it properly and replace the sensor. It will be much quicker and safer that way.

Thanks a lot for the help! I took it to the workshop, and you were spot on. It was the interior temperature sensor. They replaced it, and the total cost was 95€. Everything is working perfectly again!