Skoda Fabia O2 Sensor Issue

Sounds like a faulty O2 sensor to me! I had a similar issue with my Opel Astra a while back. The check engine light was on, and the fuel consumption was noticeably higher. In my case, it turned out to be a bad automotive sensor. Have you checked the wiring and the plug connection to the exhaust sensor? Sometimes, corrosion or a loose connection can cause these kinds of problems. It's worth investigating before replacing the entire O2 sensor. Do you have access to a multimeter?

Thanks for your input! You mentioned checking the wiring. Is there a specific way to test the cable or plug connection? I am not sure where to start measuring. Is it possible to measure the air-fuel ratio with a multimeter, or do I need special equipment?

Yes, checking the wiring is crucial. I had the same symptoms: increased fuel consumption and the check engine light. You can use a multimeter to check for continuity in the wiring harness leading to the O2 sensor. Also, inspect the connector for any signs of corrosion or damage. While a multimeter won't directly measure the air-fuel ratio, it can help you identify if the sensor is receiving power and sending a signal back to the ECU. Honestly, if you're not comfortable with electrical testing, I'd recommend taking it to a workshop. It might save you time and potential headaches.

Indeed, the issue was a faulty connection to the upstream O2 sensor. The workshop replaced the connector and the error is gone. Cost me 95€, which I think is reasonable. Thanks again for your help!