For optimum traction, even in slippery conditions, 4MATIC all-wheel drive incorporates our advanced 4-wheel Electronic Traction System. 4-ETS can help get you going even if three wheels lose their grip. Sensors at each wheel monitor traction based on wheel speeds. If one or more wheels start to slip, 4-ETS individually brakes the slipping wheels to maintain the flow of torque to the wheels with grip. Even if only one wheel has grip, 4-ETS can help get you going and stay in control.