Prius incorrect temperature readings

Greetings. I operate a Toyota Prius as well, although the year of manufacture differs from yours. I recall encountering comparable symptoms that manifested from a cooling system impediment. Conduct a thorough inspection of the cooling grille for potential obstructions such as detritus. Validate the operational integrity of the thermostat, and scrutinize the fuse associated with the cooling fan circuit, if applicable to your vehicle's configuration. I hope this helps.

Thanks for the quick reply! When you say 'cooling system impediment,' are we talking about something like a radiator blockage, or something more specific? And with the fuse, is that a dedicated fuse just for the cooling fan, or is it tied into other systems as well?

Affirmative, I am alluding to a potential radiator blockage stemming from external factors. Regarding the fuse, its function is to safeguard the cooling fan circuit. Should the fuse be compromised, the cooling fan's operational capacity could be adversely affected, culminating in suboptimal thermal management. I recommend seeking counsel from a qualified technician for precise diagnostic assessment and rectification.

Turns out it was a fuse! A slightly corroded fuse for the cooling fan, believe it or not. Replaced it for a grand total of 52€ and everything's back to normal. Thanks so much for pointing me in the right direction!