Corolla Incorrect Fuel Composition Error

Incorrect fuel composition? That's a weird one for a Corolla. Have you noticed any changes in your fuel economy? Maybe try checking the fuel filler cap, make sure it's sealing properly. A faulty cap can mess with the fuel system's pressure. Also, when was the last time you replaced your fuel filter? A clogged filter can also cause some funky issues. Have you tried running any fuel additives recently?

Thanks for the reply! Fuel economy seems normal, nothing drastic. The fuel cap seems okay, seals tightly. I haven't replaced the fuel filter recently, it might be worth checking. I did add some fuel injector cleaner as I mentioned, but nothing else. Could a defective cable or plug connection of the component really trigger the 'incorrect fuel composition' error, as some sources suggest?

A defective cable or plug connection of the component triggering the 'incorrect fuel composition' error is indeed the most likely scenario in this case. Based on the error code and your description of the symptoms, it's definitely something to investigate. If you're not comfortable tracing wires and checking connections yourself, I'd recommend taking it to a trusted mechanic. They'll have the right tools and experience to diagnose the problem accurately. It's probably nothing major, but best to get it sorted before it causes further damage.

Thanks a lot for the advice! I took it to my local mechanic, and you were right about the cable or plug connection of the component being defective! Apparently, a wire connected to the fuel composition sensor was loose. They fixed the connection for 95€, and the check engine light is gone, and the car runs smoothly now. Appreciate the help!