The official notice
Defect
On certain vehicles, water could leak into the rear of the vehicle and build up in the spare tire wheel well. If this happens, the fuel pump control unit could short circuit and cause the engine to stall. Note: This problem could cause a check engine light to turn on, a damp carpet in the cargo area and/or the sound of water moving in the spare wheel well while driving.
Safety Risk
A sudden loss of power to the wheels could increase the risk of a crash.
Remedy
Mercedes-Benz will notify owners by mail and instruct you to take your vehicle to a dealership to inspect for water leaks and install a drain plug in the spare wheel well. The fuel pump control unit will be replaced, if necessary. To reduce the safety risk, you should regularly check for moisture in the cargo area and spare wheel well.