You truely have 14 wires if you count the floor return for every color, it may use one of those on pin five (gnd) as for your diagram to finish the set of 15. The alternative pins are regularly used for communications. As an example from vga connector on wikipedia a number of those your diagram showns as no longer connected are:. Now see if you may get an photograph on the projector through forcing a resolution you already know that it supports because you might not have the ddc channel. If that works good enough and it is no longer a trouble depart it at that. In any other case you could in all likelihood identify the final pins through measuring between ground and the ddc2 pins 12 / 15 using a scope for the duration of preliminary negotiation to check for the square clock as opposed to data. The 5v to visit pin 9 must be smooth sufficient to spot and is presumably gift the entire time.