Also be aware that on many Gm vehicles there is no actual start position wire... it is ecu controlled. The ECU monitors the drop in voltage on accessory with full voltage on ignition when the key goes into start position, and decides itself whether or not to engage the starter based on other inputs. They are wierd so a no start could be caused by anything including the ECU itself, the security system, etc. I hate to say it but take it to a dealer... they can actually see what its going on with the computer when it isn't starting.