I could post this in the general MB forum, but I trust my W209 brothers to have the best responses anyway. Occasionally, my smartkey won't work, but when it does, which is usually, it works fine, even doing the all-open or all-close functions. I've discovered that when it won't work, if I click my OTHER smartkey, for my OTHER car, then the CLK's smartkey WILL work. Doesn't that seem odd?

 

odd indeed. my kye has been working flawless unless i need to change the batteries....

thats some weird *****

 

Sometimes mine won't unlock the door when I walk up - keyless go - but it works if I move it to a different place in my pocket. No clue.

 

I also had problems with my smart keys. I changed the batteries in both keyfobs and they were acting very strange for about 2-3 weeks. Now they are fine.

 

I would do a pre-emptive battery change in all of your fobs. I had a 2004 C240 sedan that was doing weird stuff with the keys and the dealer spent a TON of time (under warranty) trying to diagnose the alarm. Nothing wrong with the car, the fob(s) just needed new batteries and all was well!