C Klasse Exhaust Noise and Error Code

I had a similar problem on my C Klasse, and you're likely on the right track. When you say error, do you mean a specific error code stored in the ECU? The flap actuator, which controls the exhaust flaps, often fails. The increased exhaust noise, especially on cold starts, suggests the exhaust flaps are stuck open. They should close on startup to warm the catalytic converter faster and reduce emissions. If they're stuck, you'll notice the noise. Can you share the specific error code? It should help narrow down the problem.

I should have mentioned the code. The error code is P0444 - Evaporative Emission Control System Purge Control Valve Circuit Open. I was focused on the noise and didn't think it could be something else. Does that change your assessment?

P0444 is an evaporative emission control system issue and not directly related to the exhaust flaps. Sorry, I was too focused on the exhaust noise! While the exhaust flaps could still be contributing to the noise, the P0444 code indicates a problem with the purge control valve circuit. There could be multiple issues or the noise is related to something else. Given the error code and the potential for misdiagnosis, I suggest taking it to a workshop. They can properly diagnose the exhaust noise and the P0444 code.

Thanks for the insight! I was stuck on the exhaust flaps. I'll take it to a workshop for a diagnosis. It was the purge valve, as you suggested, plus a small exhaust leak near the catalytic converter, which explained the noise. The flap actuator was fine. Cheers!