onstar fuse location

[cmc76]

got a superchip tuner, cheap, i went to install, tells me i need to pull onstar fuse.
google give me the same runaround and " are you afraid of big brother" responses.

which box, underhood or in dash. a number would be helpful. 04 tahoe z71.
thanks

 

[cmc76]

ok, found the info fuse, its shown in many of the manuals.
during the install, i get an application not supported error 038.

any ideas?