Arkana exhaust treatment malfunction

I had a similar issue with my 2018 Opel Insignia. Check engine light, exhaust smell... Does the exhaust sound louder than usual? It could be a defective lambda sensor causing an exhaust leak. Have you checked for any visible leaks?

Yes, the exhaust does sound louder. Where exactly should I be looking for the leak and how can I check the lambda sensor?

Given the symptoms and louder exhaust, I'd suspect the leak is near the exhaust manifold or catalytic converter. Visually inspect for cracks or dark soot deposits. Testing the lambda sensor accurately requires diagnostic equipment; it's best to take it to a workshop. It was the lambda sensor in my case.

Thanks for the advice! I took it to the workshop and you were right, it was the lambda sensor. Repair cost 375€. Appreciate the help!