A specific, well-known M157/M278 failure is oil wicking through the cam position sensors and siphoning into the ECU harness, turning a cheap serviceable item into a potential five-figure repair. Owners advise checking the sensors at every oil change; the fix can be as simple as cleaning the harness connector with contact cleaner.
Cam position sensor leaks and oil in the ECU
Mercedes-Benz E63 AMG (W212) · mechanical