Fuse TBC 2B ? 04 Silverado

My 2004 Silverado Crew Cab 4wd repeatedly blows the 15A fuse listed in the manual as one of the Truck Body Controllers showing up as TBC 2B on the fuse diagram.
I don't have a dealership in the area to have the thing scanned with the GMC scanner and the generic one doesn't come up with any errors.
Does anyone have information on what (other than my instrument cluster and 4wd indicator lights that keep going out) would be on this circuit to check for a short?
If I change the fuse, it can go a couple of weeks without blowing but the last one I changed blew within 5 minutes. Never the same but always eventually blows.
Thanks,
Gord

Does anyone have the wiring diagram that would show what all goes on this circuit? I hate to drive for over an hour to the closest GM garage if it could be simply trouble-shot.
Thanks

looks like by google that it controls a lot- dome lights to your blower. sorry can't help. good luck.