Hello,
I must preface this response by advising on what CAN-BUS means. Just like the router at home that projects wifi through the house, and connects all of the devices in the house, the CAN-BUS system is a way for vehicle systems to link and communicate.
You likely have an error in the CAN-BUS system, where the engine control unit is not connecting to the COMMAND system.
There may be a loose connection, a bad fuse, faulty wiring, or a bad control module for the engine, command system, or any control module in between.
Mercedes Benz takes full advantage of the CAN-BUS system, as they are one of the most complicated in the industry. I advise you to use a certified facility, with the factory Mercedes diagnostic software, specifically. Diagnostic costs may be much higher if you use a non-factory trained technician, or a shop without the proper software.
Here is a list of certified shops in your area, and you should look for European or German specialists: http://repairpal.com/mercedes-benz-within-10-miles-of-palmdale-california-93550