Wiring question on 88 Pete

The auxiliary wire for the trailer plug or what would be the Trailer ABS wire in newer trucks. Someone told me its the blue wire going into the firewall of the trailer harness. I found that but they all turn white on the other side of the plug inside the cab. Does anyone know if this wire actually goes into the fuse panel and which fuse it would be on the panel and where it goes after that if it does. I'm guessing its unused on this year truck but I'm trying to put a switch in the dash to make it hot for my sweep tarp in my trailer. I've searched wiring diagrams but all I can find are ones for newer 379's which would probably have Trailer ABS modules. Any help would be appreciated. Thanks!!

 

Yea I looked.. Found a few dead end wires but nothing tagged.... Would anyone know what the fuse would be called on the panel for this wire??

 

Yea I thought about making it hot somehow and testing wires... Thanks for the tips

 

Do I think that would actually have a fuse in or just an empty hole in the panel??? I mean I no someone could've stuck one in the spot over the 24 year life of the truck but I'm guessing the dealer would've left the fuse out since they didnt actually use the wire for anything

 

I just can't believed they wouldn't have labeled it somehow on the fuse panel... None of them say trailer anything... Just a few spare SW... Which I'm guessing means spare switch