Vauxhall Vectra NOx Catalyst Error

Sounds familiar. I had a similar issue with my old Peugeot 307. Check engine light, NOx emissions error… turned out to be a leak in the exhaust system before the catalytic converter. Is the exhaust particularly noisy?

Thanks for the quick response! The exhaust isn't drastically louder, but I can definitely hear it more than usual, especially when the engine is cold. Where exactly was the leak on your Peugeot?

On my Peugeot, the leak was near one of the joints in the exhaust pipe, fairly easy to spot once I got under the car. Given your symptoms, I'd strongly suspect a similar exhaust leak is your culprit. You'll probably need a new exhaust section or a weld repair. Worth getting it checked at a workshop.

Thanks for the advice! I took it to a local workshop, and you were spot on – a small crack in the exhaust manifold. They welded it up for 265€. Hopefully, that's the end of that. Appreciate the help!