Vectra oxygen sensor issue

I had a similar issue with my old Renault Megane. Same symptoms – check engine light and increased fuel consumption. The error code also pointed to the oxygen sensor. Did you check the wiring harness for damage or corrosion?

I visually inspected the wiring harness near the O2 sensor, but not in depth. What should I look for beyond obvious corrosion? Any common failure points to focus on?

My mechanic found a broken wire inside the harness, very close to the connector. It was hard to spot. Given the symptoms, error code, and that you've checked the sensor, I'd advise having a professional take a closer look.

Took it to a workshop, and it was a defective connection to the oxygen sensor, as suspected. Repair cost me 95€.