I see that you are reading the service manual word for word. Its says hook up the HDS or in your case the snap-in scanner. Short the SCS conector.
In the HDS function menu you need to actually activate this by clicking on it. I am not familiar with the snap-on scanner so i cant tell you where to go in the menus to find it. It may not even be possible with it. Just plugging the scanner up to the car wont do what you are thinking it should.
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If your happy with my services please
ACCEPT. dont forget about feedback. I want to know what you think
If it says offline Im probably doing something else but i do check back periodically.
Dont forget those BONUS'S.