Wiring Schematics sources for body wiring on trucks?

Wondering if any of the mechanics on here have found a good source for body wiring schematics on trucks?

We have pro-demand for heavy trucks here at work, but I find a lot of the time I don’t get everything I need.

Right now I’m trying to find out what pins on the body harness correspond with what on the truck, so I’m looking for something to identify the pins on the harness that plugs into the firewall.

There’s been a few occasions where I’ve been looking for this, so I’m wondering if anyone knows of a general source where I could find things like this as apposed to calling the dealer or whoever every time.

 

Point me in the right direction then...

 

Point me in the right direction then...

 

Yes, I understand this, and that is fine. We do deal with whomever we have to in order to get this info.

I’m just wondering if there is some online source similar to Mitchell, or say SIS for CAT engines, or QuickServe for Cummins, that would allow me to log in & find body wiring diagrams, plug schematics, and whatever else for the trucks. Mitchell works for the most part, but when I’m trying to find a pin on the firewall at the harness that corresponds with whatever it is I’m doing it’s much easier to have a print out.

Dealers & support work fine most times, but sometimes it’s a headache trying to get what you are looking for too.