Seat Mii Check Engine Light and Fuel Consumption

Sounds familiar. I had a similar issue with my Mii: check engine light, sluggish performance, and increased fuel consumption. Could be the exhaust temperature sensor. Have you checked for exhaust leaks? When does the check engine light come on? Immediately after starting, or after driving?

Thanks for the quick reply! I haven't spotted any leaks, but I can't check underneath properly. The check engine light usually appears after driving for 15-20 minutes. Does that sound like your experience?

That sounds like what I had. The light coming on after driving suggests the temperature sensor needs to heat up before throwing an error. This could mean it's not reading correctly due to an exhaust leak, or the sensor itself is failing. I'd recommend getting the exhaust system and sensor checked by a workshop. A faulty sensor can mess with your emission control system.

Took it to the shop. It was a faulty exhaust temperature sensor, likely from a small exhaust leak. Sensor replacement and exhaust system check cost 265€ Thanks for the help!