Aygo Exhaust Treatment Malfunction

I had a similar issue with my Aygo. Is the smell like unburnt fuel? Check your exhaust pipe for leaks before suspecting the lambda sensor. A cracked catalytic converter could also trigger those symptoms. Any recent work on the particulate filter?

The smell is similar to unburnt fuel. I will check the exhaust pipe for leaks. What were the fault codes when you experienced the issue? Did you check the NOx sensors?

My fault codes pointed to the lambda sensor, but the cracked exhaust manifold was the root cause. A proper diagnosis needs a smoke test. It's best to have a workshop check it.

Thank you for the information. I followed your advice and took it to a workshop. It was indeed a defective lambda sensor, and the repair cost 375€.