Peugeot Expert NOx Catalyst Aging Due to Exhaust Leak

Indeed, an exhaust leak upstream of the NOx catalyst can absolutely lead to what seems like premature aging. Think of it as trying to bake a cake in an oven with a broken door – the temperature is inconsistent, and the results are never quite right. Is the leak significant? A minor leak might only marginally impact the catalyst, while a larger one could severely disrupt its function.

That analogy is very helpful. The leak does seem fairly pronounced, audible especially during cold starts. So, if uncombusted fuel and air leak before the catalyst, this causes it to operate outside its optimal range and appear aged because it does not work as expected?

Precisely. The leak allows unmetered air and possibly unburnt fuel into the exhaust stream before the catalyst, altering the air-fuel ratio and temperature. This can overload the catalyst, causing it to function outside of its designed parameters, thereby reducing its efficiency and mimicking the symptoms of an aged or damaged unit. Eventually, the error memory will show an issue with the emissions system. I would suggest bringing the car to a workshop.

Thank you for confirming my suspicions and for the clear explanation. I took it to a workshop; it turned out to be a cracked exhaust manifold. They replaced it, and the error disappeared. The total repair cost was 265€. Your advice was invaluable.