Mercedes B Klasse exhaust treatment malfunction

A faulty lambda sensor can definitely cause those symptoms. I had a similar issue with my old car, though it wasn't a Mercedes. Rough running and engine light were the first signs. A bad lambda sensor messes with the air-fuel mixture, which can then overload the catalytic converter and maybe even the particulate filter if your car has one. Exhaust leaks are concerning though; I would check the exhaust pipe itself for damage. Have you noticed any change in fuel consumption? What error codes are you getting?

I appreciate your insights. Regarding the error codes, I will retrieve them shortly. However, could a faulty lambda sensor directly cause an exhaust leak from the exhaust pipe, or should I consider this a separate, potentially compounding issue?

While a malfunctioning lambda sensor won't directly cause a physical leak in the exhaust pipe, the incorrect air-fuel mixture it creates can lead to increased stress on the exhaust system due to higher temperatures or unburnt fuel igniting in the exhaust. This might, over time, accelerate corrosion or damage to the exhaust pipe, especially at the joints. However, given you already have a strong exhaust smell, engine light, and rough engine running, and you suspect a faulty lambda sensor, it's best to have it professionally checked. It could be the root cause, or there might be additional issues like a crack in the exhaust pipe itself. Ignoring it could damage the catalytic converter or the particulate filter, resulting in much higher costs.

I appreciate your advice; I will proceed with a comprehensive inspection at a reputable workshop. The anticipated repair cost for the lambda sensor replacement is approximately 375€. Thank you for confirming the potential impact on other exhaust components; your insights were indeed valuable.