I have heard that magnets anywhere around the vehicles computer system can be damaging to its function. If this is fact, then would a magnetic sign placed on the passenger and drivers door be a problem for the functioning of the computer? Or is it placed far enough away so that it does not interfere with it.

 

I would not worry about a door sign. Its more about having magnets near your GPS or Compass that will mess things up, but the door is plenty far away.