Peugeot Partner check engine light and fuel consumption

Hey there! I had similar symptoms on my Partner: check engine light, higher fuel consumption... Sounds like it could very well be the oxygen sensor before the catalytic converter. The oxygen sensor helps determine the air-fuel ratio, and when it fails, the engine computer won't be able to set the optimal mixture. Did you check the cable and plug connection to the sensor?

Thanks for the quick response! No, I didn't check the cable and plug. Where exactly is that located, and what am I looking for?

It's usually easy to spot. The oxygen sensor is screwed into the exhaust pipe before the catalytic converter. Trace the wire coming out of it; you'll find the connector. Check if it's loose or if the cable is damaged. If everything seems fine there, it's most likely the sensor itself. I'd recommend visiting a workshop; they should be able to diagnose it quickly.

Thanks for your help! Turns out it was indeed the oxygen sensor cable. The workshop replaced the sensor and the associated cable, and the whole repair cost 95€. Everything is back to normal now.