I finally ended up buy a 2016 (W212) E350 last month. It came with about 29K miles and so far im loving every minute of it. The dealer was shameless and didn't give me a spare key or the keyless start button ( and neither any gas). So I got the key cut at the local Steven's creek MB in santa clara, CA and then decided to buy the keyless button on Amazon. I plugged it in and pushed it in a few times and it got itself coded. PRetty impressed with myself!


So if this helps.

 

One trick with keyless go I did lately to my friend, who is electronic boards designer.
We stood up next to my car door, who was open.
I closed the door, touched outside handle and car honk to confirm lock.
I stepped 5 steps back and ask my friend to open the car. It was locked.
So I made 5 steps to the door and open it without a problem.
He is cold blooded person, but could not help asking "how the car knows its you?"
Plenty of original start buttons on ebay.
Enjoy

 

For a MB dealer it is totally under performing to sell a Mercedes with only one key. The cars they sell should always come with two keys.

I have posted about this in another thread. Some insurance companies (probably most of them) require you to show two keys if your car is stolen. If you only have one key you may have some hard time to get coverage for it.

My car of year model 2010 can have four keys at the same time programmed for it to work. I only have two. While the car was still under warranty the key I used went bad and the dealer got a new key for me programmed to work with the car. They also removed the old key from the car’s programming.

Any decent MB dealer should have the MB vehicle they sell, new or used, come with two keys and only those programmed for the car to work with.