I don't have 2008 prints but do have 2009. If it helps, here you go. A Brown/Gray wire coming out of the 15 amp Battery fuse supplies Direct power to the TSM/TSSM/HFSM module Pin #1.
From there it then goes to Pin #5 of the Speedo,, Then to Pin #5 of the Tach (if you have one). Also to Terminal A of the optional Siren.
That's it for the 15 amp Battery fuse. If you have an optional Siren, that would be the 1st place to look. The back up battery is probably shorted.
You did not say how much of a current draw there was. That would give you a clue as to what is going on.
Remember, the above applies to a 2009 but most likely is the same as a 2008.
Good Luck!