DS4 Oxygen Sensor Fault

Those symptoms – check engine light, error, and more fuel – do sound like an O2 sensor problem. A bad cable or plug could cause it by messing up the signal from the sensor. Not sure if the sensor itself is bad or just the connection. Did you check the wires and plugs for damage?

I checked the wires and plugs, but they look fine. The OBD2 scanner says it's the oxygen sensor. Could it be something else, or should I just replace the O2 sensor?

Since the OBD2 scanner points to the O2 sensor, and you checked the connections, replacing it makes sense. But, to be sure that's the only problem, a shop visit might be a good idea first. They can check for other issues, but it seems less likely.

I went to a workshop, and they found a bad oxygen sensor cable. The fix was 95€ for parts and labor. The check engine light is off, and the fuel use is back to normal. Thanks for the help.