Hello hope everyone is doing well. I have 2020 C63s sedan done around 30k kms on it. Today while driving in Sports + i noticed all of a sudden it had lost all sound while downshifting in all gears. Pops and bangs are still there stock when i lift my foot in any gear arounds 4-5k rpm. Is there any particular reason this happens. The car is parked and haven't driven it again i hope it goes away when i drive it tomm. Has anyone encountered this issue before, if not your advice is welcome.

 

This actually happened to me a couple of months ago.
I was driving around and suddenly the sound on downshift disappeared.

I kept trying to downshift but still no noise. So I pulled over and restarted the car and the sound came back right away.

I tried to search online but couldn’t find anyone having the same issue, it’s never happened again since.

Try taking your car out again, hopefully it should come back.

 

The only thing that comes to mind is one of the three exhaust flaps have said goodnight and one of them is stuck in quiet position. Lets check the rear mufflers first.

Can you get a torch and check if the flaps in both the rear muffler's flaps are opening and closing when you press the exhaust button on the center console?

 

Sounds like soft limp mode, this is reported on the E 63 S side as well, there might be a stored code, maybe a sensor glitched out putting the car in soft limp mode, it is common but usually clears itself or you might have to clear the code manually.