15 pin VGA configuration
A standard PC will use that bidirectional data pin for detecting display presence and for determining what resolutions it supports. If you omit that pin, the PC most likely is not able to even detect when the display gets plugged in, or if it can detect that, it won't be able to determine what resolutions it supports. So most likely, there will be no picture. Not unless you have a professional video card whose drivers support forcing the interface enabled with fixed resolution, so it will output a picture even if display is not present.