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 SL600 Wire Connector on Transmission May Leak Fluid and Damage Control Module
Mercedes-Benz SL600 Problem
Visitor, 2004 Mercedes-Benz SL600, 48,000 mi
Twice my '04 SL600 went into "Limp home mode" effectively without transmission function. The dealer replaced the transmission's "Conductor plate" and sent me along my way.
Mercedes Benz was once a quality product which we paid handsomely for. Now the brand is suffering from all these failures and "brand loyalty" will not keep MB owners from falling into the arms of LEXUS.