Engine oil can leak into the engine wiring harness from the cam adjuster solenoid. The oil can migrate through the wires and possibly damage the engine control unit. A leaking adjuster solenoid should be replaced.Google+
Car Problem Reports
Mercedes-Benz C230 Oil From Cam Adjuster Solenoid May Leak into Engine Wiring Harness
Mercedes-Benz C230 Problem
Average Mileage: 120,000 mi (90,000 mi - 150,000 mi)
This pesky little part is hidden under a plastic cover at the front top of the engine, and most mechanics not familiar with these cars would not know to look under there. Luckily my Mercedes mechanic checks these (apparently they fail with some frequency) and they caught it. Oil leaks through the seal and gunks up the wiring, eventually causing electrical problems. If the oil gets into the computer unit you'll have to replace that too for much money. You may need to have the engine harness replaced if the oil contaminates it too much. Luckily I was able to clean up the wires and connection to avoid this.
Visitor, 2002 Mercedes-Benz C230, 90,000 mi
recall fixed it under warranty.
3500 dollar job