Technically I am pretty sure that Auto Open and Auto Close are misnomers as there are not discrete signals for open and close. What is really happening is that the car sends a "Toggle Door" command to your garage door opener under either the Auto Open or Auto Close. Doesn't your garage door have a safety "electronic eye" that causes the door to immediately stop if the beam across your door is broken (edit - these have been required for all openers made in the US since 1993)? If you don't then you should replace it - these have been standard for many years and are required for the "smart" garage door openers like the Chamberlain MyQ system.