Etios fog sensor malfunction

Sounds like you've got a bad connection somewhere. The fog sensor talks to the ECU (Engine Control Unit), which then controls a bunch of other stuff – A/C, mirror heating, even the windshield washer jets because the ECU will try to stop them freezing in low temperatures. Have you checked the connections to the sensor itself? It's usually located near the rearview mirror, behind the plastic housing.

Thanks for the info! When you say "connections", are we talking about the plug going into the sensor itself? Is it easy enough to get to? Don't want to start pulling things apart if it's a bigger job than I can handle.

Yeah, the plug and the wiring right near the plug. It's a common spot for corrosion or damage. The plastic housing should pop off with a little persuasion, but be gentle. If you're not comfortable, honestly, it's probably worth taking it to a workshop. My local guy said it's a pretty quick fix if it is just a connection issue, so shouldn't cost a fortune.

Okay, thanks a lot for the advice. I think I'll take it to a workshop. They quoted me 95€ to fix it. Sounds like the connector is the problem, like you said.