The claim is that some cars monitor the lights and indicate on the dash if a light bulb is out. It does this by monitoring the current pulled by the lights and it knows when a light is out due to the light pulling no current. Since LED lights pull much less than then non LED bulbs, the sensor would see this as a light out. The Canbus error free lights have resistor in them that makes the sensor not report the light as out. I don't think Smart's have that sensor.