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.
Car Problem Reports
Mercedes-Benz SLK230 Wire Connector on Transmission May Leak Fluid and Damage Control Module
Mercedes-Benz SLK230 Problem
Average Mileage: 89,100 mi (58,200 mi - 120,000 mi)