When I installed my Atoto radio the wire for the dimming of the radio was uncorprated in the Metra wiring harness I bought that matched the Fortwo. But as usual the Fortwo is a horse of a different color and Smart does alot of things different. The dash illumination is lighted with LED's and they are a lower voltage than a standard T10 automotive bulb. Can bus controls the lighting and the ciip that controls the dash lights wouldn't supply the 12 volts that my radio needed to dim itself when I turned on the headlights. I ended up cutting the wire out of the Metra connector and I ran a wire from the parking light in the headlight assembly clear inside the car and spliced it to the illumination wire on the radio. That way the radio got the full 12 volts and when I turned on the parking lights the radio dimmed as it should. If I would have applied 12 volts to the illiumination wire and had NOT disconnected it from the harness I would have undoubtedly blown out the chip that supplies low voltage to the dash cluster.
I learned the Can bus system early on. When I bought my Fortwo it did not have the dash pod clock or tach. I bought them used off from ebay. But when I got them they were missing the wire that connects them both to the dash cluster for them to work. So in my zeal to install them and my ignorance of Can Bus, I thought I would go ahead and hook up the clock. The clock had 3 wires coming from it so I surmized that there was a Hot wire for power to the clock, a ground wire for the clock, and a Illumination wire to light it up at night. I went to my work bench and got out my 12 volt power supply and in shooting 12 volts to the clock I ruined it. So I ended up buying another clock and it was from a 2005 Fortwo, so I had to make a change of 2 of the wires to make it work. But the pods run off of Can bus and they never recieve 12 volts, analog wiring does not apply to the Fortwo. Disconnect your battery for a few seconds and then reconnect it and you will hear your tach and clock spin up. So I learned the hard way that NOTHING is conventional on the Smart.
Try to find your switch that turns the dome lights on and off when you open or close the door. They are integrated into the door latch mechanism. When you flip a switch it doesn't necessarily mean you switched on or off 12 volts. You're sending a low voltage signal to the SAM to switch something on or off. So tread lightly whenever you add something to the Fortwo because it can cause problems. I have had many problems over my Android radio with the Smart, and Atoto has agreed to replace my radio with a newer version with better WiFi and less voltage drain, so I'm going to take the radio out again, but thank goodness it will be plug and play this time. DCO