I am trying to sell my 94 Saturn SL2 and someone told me that it has blow by. What is this and what does it mean? How do you fix this problem? Any help that you can give me on this would be great! Thanks!

My daughter, a continent away from me, drives a 1995 dodge Caravan minivan. According to her, recently she has a dash light indicating that a door is open. This is coupled with a ringing bell and the interior lights flashing. Needless to say the door is not open. I have had a similar problem with a 1995 Ford Windstar van. Thanks to someone in this forum the solution was cleaning the copper contacts on the sliding side door and the door frame. I do this perodically as these things tarnish and start the sequence of warnings. I have to believe that the dodge van which my daughter drives has a similar problem . Any advice out there??? The distraction is driving my daughter nuts and before she gets a service call I thought there might be an easy solution.