If your car is pinging, get it to a tech immediately! Your car is equipped with knock sensors, so long before you would ever actually hear a ping the timing would be so retarded that it'd never present itself.
Knocking is typically a result of carbon buildup, which the M119 is prone to if not driven aggressively regularly. I just went thru all this with my 500E, but never once did I hear an audible ping/knock/predetonation.
All the best, Michael