Skoda Citigo Engine Light and Exhaust Smell

The engine light and rough running, coupled with the strong exhaust smell, definitely point towards a problem in the exhaust treatment system. Given the mileage, a defective lambda sensor is a strong possibility. When you say 'exhaust leaking', can you pinpoint where it's coming from? Is it near any of the exhaust pipe joints, the catalytic converter, or perhaps around the NOx sensors? Knowing the location of the exhaust leak could help narrow things down.

Thanks for the quick reply! The exhaust seems to be leaking from somewhere around where the exhaust pipe connects to the catalytic converter. Does that change your opinion at all? Is there a way to test the lambda sensor without just replacing it?

The location of the exhaust leak near the catalytic converter certainly reinforces the possibility of a faulty lambda sensor. While there are diagnostic procedures involving multimeters and oscilloscopes to test lambda sensors, they require specific tools and knowledge. Considering the symptoms and the location of the exhaust leak, it's highly probable that the upstream lambda sensor is the culprit. It might be best to take it to a workshop for a proper diagnosis and replacement. Continuing to drive with a faulty lambda sensor can damage the catalytic converter over time.

You were spot on! Took it to a trusted mechanic, and it was indeed the upstream lambda sensor gone bad. New sensor fitted, engine light is gone, and she's running smoothly again. The exhaust smell has also disappeared. Cost me 375€, but it's worth it to have my Citigo back to its best. Thanks for your help!