The electrical connector at the automatic transmission may leak fluid. Over time leaking fluid could migrate through the wiring harness and damage the transmission control module. If that happens a new harness and control module may be necessary to correct the problem.Google+
Car Problem Reports
Mercedes-Benz S500 Wire Connector on Transmission May Leak Fluid and Damage Control Module
Mercedes-Benz S500 Problem
Average Mileage: 82,333 mi (54,000 mi - 118,000 mi)
The shop replace the electrical connector and the car is leaking again. They are still trying to figure this out.
This was a $15 rubber grommet. My indy shop did not even charge labor, they said it was so easy. It caused me no performance problems or other damage, but I did get it fixed within days of noticing a drip in the driveway. I've gone almost 40,000 miles since with no problems.