Peugeot 508 Oxygen Sensor Issue

Whoa, sounds familiar! I've got a 508 too (not the hybrid though), and had a similar problem. The malfunction indicator was driving me nuts, and the error memory was full of oxygen sensor codes. Did you try checking the sensor's wiring?

Wiring, eh? I'm no grease monkey, but I can poke around a bit. Where exactly should I be looking? Is there a specific plug or connector that's prone to issues?

Yeah, the connectors! In my case, it was a loose connection on one of the oxygen sensor plugs. Caused all sorts of havoc with the air-fuel ratio, apparently. Honestly, unless you're super confident, I'd just take it to a workshop. Could save you a bigger headache down the line. They have the gear to properly test the sensor and wiring.

Cheers for the advice! I wiggled a few wires and, yeah, not my cup of tea. Dropped it at the shop; turns out it was a defective cable/plug just like you said! Cost me 95€ for the fix. All sorted now!