Hello, when you say it would go into “D” & “R” do you mean the visual letters on your dash, or the shift stick wouldn’t move, or do you mean the car wouldn’t physically move forward or backwards?This problem has nothing to do with whether your foot is on the brake or you've done a "teach in" for your transmission. I tried all that.
The actual solution is to make sure the latest version of firmware is installed in your Smart's Transmission Control Unit (TCU) -- BB Benz is correct in making this clear.
My Fortwo stopped dependably going into R or D a few days ago. It's last firmware update had been back in Feb. 2009, so after reading this forum, I called the dealer to arrange an upgrade. They tried to thwart my effort by saying I should pay several hundred dollars for a full tranny diagnostic, but eventually I prevailed. They charged me $110 (the $10 for "consummable shop supplies" - can you believe it?) to hook it up tho their computer and install the latest firmware. (They wouldn't tell me if it's v2.03 or what, just that it's the current version.)
Result: Tranmission problem solved -- it goes into R and D every time now. My heartfelt thanks to BB Benz and others here. Cheers.
Thanks in advance.