E Klasse Check Engine Light and Exhaust Smell

Sounds familiar. I had a similar issue with my old Volvo. The engine light kept coming on, and the exhaust smell was awful. In my case, it ended up being the catalytic converter, not the sensor. Was the particulate filter checked? Exhaust leaks make those engine lights come on for all sorts of reasons. It's a bit of a guessing game, but what kind of diagnostic checks did you perform?

The diagnostic pointed towards the lambda sensor, but you're saying it could be the catalytic converter too? How did you figure it out on your Volvo? Any other specific symptoms you remember?

For the Volvo, the initial diagnostics suggested a sensor issue as well. But the mechanic checked the catalytic converter and found it was completely shot. The rough running and smell were both due to that. Considering you have an exhaust leak too, it might be worth having the catalytic converter checked. Otherwise the engine light may come back on soon after replacing the lambda sensor. But without checking it's hard to be certain. You should go to a workshop.

Alright, thanks for the insight. I'll definitely have them check the catalytic converter then. Ended up getting the lambda sensor replaced and exhaust leak fixed. Total cost 375€. Runs much better now.