Peugeot 107 NOx Sensor Exhaust Leak

That's a fairly common issue on these Peugeots, especially with that kind of mileage. Where do you think the exhaust leak is coming from? Have you had any work done recently on the exhaust system or catalytic converter? It could point to the root cause, or maybe just be a symptom.

The exhaust leak seems to be near the catalytic converter, but I can't pinpoint it. I haven't done any recent work on the exhaust system or catalytic converter. Could the catalytic converter failing cause the NOx sensor failure, or are those separate?

Okay, exhaust leak near the cat and a NOx sensor failure... they could be related. A failing cat can definitely throw off the readings from the NOx sensor and trigger the check engine light. It’s a bit of a grey area without seeing it, to be honest. Given everything, I’d recommend a professional diagnosis. It might save you money in the long run compared to throwing parts at it, especially with pollution control stuff.

I took your advice and saw a mechanic. It was a defective cable, and the total was 95€.