Hi,
I read through the wiring schematics. I suspect you lost the main power supply from the under-hood fuse box. Everything you mentioned (down to the trailer brake) is powered by a 175 amp alternator fuse.
If you look at the pics below, I highlighted everything. Now, if you haven't already, check to see if there is power at the circuit breakers. I suspect there is none. The click you are hearing is most likely the primary side of a relay closing the circuit, but there is no power to send to the component from the secondary side.
In the pics, I started at the components and worked backward to see what powered them. Check all the main fuses. Also, make sure they have power to and from them. I suspect that when you connected to the trailer.
Here is a link you may find helpful:
https://www.2carpros.com/articles/how-to-check-a-car-fuse
Let me know what you find.
Take care,
Joe
See pics below. Note: The 175 Amp fuse is not in the regular under-hood fuse box. It's in what they call a fuse holder. It is on the passenger side of the fire wall.
Images (Click to make bigger)
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Wednesday, June 15th, 2022 AT 10:33 PM