Have Dash ABS light & "El Traction S" message but no abnormal braking.

I had a similar experience. When those lights go on, does the cruise control able to function? If not, you need to replace a sensor unit located behind the brake paddle on top of the paddle which solves that problem. A Mercedes Benz mechanic told me about it. I bought sensor from Mercedes and had a mechanic install it for me cheaper than at the dealership! It worked!!!! Good luck!