Peugeot Bipper Oxygen Sensor Issue

Yo. Yeah, a bad O2 sensor can definitely mess with your fuel trims. The ECU uses the O2 sensor data to adjust the air-fuel ratio. If it's sending garbage, the engine could be running rich, hence the higher fuel consumption. Have you checked the sensor's plug connection? Sometimes a loose or corroded connection can cause intermittent issues before the sensor completely fails.

Thanks for the quick response! You mentioned the plug connection. I visually inspected it, but is there a way to test it properly? Like, with a multimeter or something? I'm kinda novice at that, but I'm willing to learn if it saves me a trip to the shop. Also, is it possible the catalytic converter is also involved? Could a bad cat cause similar symptoms?

You could back-probe the connector with a multimeter to check for voltage and continuity, but honestly, unless you're comfortable reading wiring diagrams, it might be tricky. And yeah, a failing cat could cause similar symptoms, but given the error code specifically points to the O2 sensor, and you're seeing increased fuel consumption, it's far more likely the sensor itself or its wiring. At that mileage, they often degrade. I'd recommend getting a proper diagnostic done at a workshop.

Okay, thanks a bunch for the advice. I think you're right; it's probably best to take it to a workshop before I mess something up even more. I just got it back from the garage. The mechanic found a defective cable to the oxygen sensor. They replaced it, and the check engine light is off and my fuel consumption is back to normal now. The repair cost me 95€ in total.