Seat Formentor Oxygen Sensor Issue

Your situation with the Seat Formentor is similar to one I had before. The check engine light and reduced fuel efficiency suggest a bad oxygen sensor. The engine is trying to tell you it's not breathing right. The error code reinforces this. Have you checked the O2 sensor's cable and plug connection for damage or corrosion?

When you had the issue, was the bad cable obvious, or did you need special tools to find it? I'm trying to figure out how much work this will be.

In my case, the cable looked fine, but there was corrosion inside the connector. It's like a leaky faucet: the problem isn't obvious, but the effects are. Given the mileage and the error code, I'd suggest a qualified workshop for a full diagnosis.

It was the O2 sensor. The cable connection was faulty. I replaced it for 95€. The check engine light is off, and I expect my fuel efficiency to improve. Thanks for the help.