If you find the wire under the hood it should not be connected to anything and then you put your volt meter on continuity check. Then when you touch the leads it will beep.

So if you have it connected under the hood and use that wire you mentioned earlier you can touch what you think is the pass through wire and it will beep when you have the right one.

Can you take photos of what you are using and seeing?

 

So after looking at the area again I found these 4 blunt cuts. They don’t look like the correct color codes but the one in the middle is thicker & seems to consist of multiple wires. Maybe the correct wires are in there. I’ll start taking them apart but I’m not very hopeful.

 

The wire in front not middle.

 

Going back to the dealer for oil change, recall, etc. Will have them look for them & prove to me the pass thru wires were actually installed at the factory. I’ll pay for their time if they find them, it will be worth it.

 

Those blunt cut wires look like pass through wires.

Should find the other end of those under or very near the relay box under the hood,

 

I thought they were pass thru wires too until I untaped them. Three are the wrong colors for pass thru wires & the fourth is actually a small bundle of wires none of which are the correct colors.