Horn relay

[TBone]

I'm installing an air horn on my 06 Sierra 2500 and am trying to locate the horn relay. Any ideas where it's at before I starting taking my dash apart?
Thanks! Tony

[Mike]

I would think that relay is in under hood fuse box. Labeled as horn.

[madmaxdmax]

I would think that relay is in under hood fuse box. Labeled as horn.

X2 in the big black square plastic box under the hood ...drivers side:thumb:

[TBone]

You guys are geniuses. I guess I should have tried the obvious first!
Now I need to find which wire it is.
Thanks! Tony

[TBone]

I have a PDF copy of the full wiring diagrams for a 2006 GMC Sierra 2500 if anybody wants a copy.