I thought i'd share this with everyone. I recently started having an issue with my Crossfire:
1) Doors only locking/unlocking when they wanted to.
2) Hatch only locking/unlocking when it wanted to.
3) Key fob would make the lights flash (like it is suppossed to) but wouldnt lock or unlock anything.
4) Gas tank lid wouldn't pop up for me to put gas in.
5) Lights- sometimes when the car was turned off, one light would come on and not go off causing
the battery to drain if it happened in the middle of the night). Sometimes the lights would flicker.
6) Random dash lights would come on: Check Engin/Tire Pressure/some i still dont know what they mean

All of these problems were due to the "central locking vacuum pump" not working. Apparently my back tail light had a leak. When it would rain, the water would drip down onto the flooring of the trunk/hatch. This part happens to be located underneath the flooring. Once this was replaced- EVERYTHING started working perfect.

They had to replace this pump and have it programed to my car. I'm told you can't get this part off of another car because once it is programed to a car, it can't be reprogramed to another.

Here is the part #
Mercedes part- #17080000848 (it cost me $575.95 plus $125.00 to have it programed to my car).

I hope this helps someone out because it took me a few months of research to figure out what my problem was.