Sounds like it doesn't have the data set for that model.

 

Go to your account, click on "your issue" then “new issue”. Go from there.

Have you tried other scanners? Do they communicate? The key is on yes? It could be a connector problem in the car.

 Tell us about your 38 pin adapter. If it is a cheap one from ebay or similar, they are not fully wired inside and will not get you into most modules.

 My experience with adapters such as that one is that only the k line for the engine control computer is wired, thus you would be able to access that system but none of the others. I even purchased one on ebay that claimed to be more fully wired (they showed a schematic in the listing) only to find upon opening it that only one k line was wired. I sent that one back. I then purchased a 38 pin adapter from germany (along with a serial extension cable) intended for the Autel EU702 scan tool, which is the previous generation tool, with the hopes it would get me into more systems. I've not had a 38 pin mercedes to test it on yet unfortunately so I have not much more to add.

 Hello Sir, how is the issue now? Is it solved or it's returned back to dealer?

 the only 38 PIN adapter that works is the autel db15 femaled 38 pin adapter for MB.  it is color red with a big flat box at one end.  You will also need a autel db15 male to male cable to connect to the MD802.  With this adapter, the MD802 will read all modules it was designed to scan.  Cheap adapters do not work as only 3 or 4 wires in them are connected.  Do NOT buy the very expensive autel CONKIT - it does not work.  Was also a frustrated user just like you until we purchased the above unit.  Now, MD802 works with all our MB - those with 16 pin port and those with 38 pin port in engine bay.  Hope this helps.  good luck.