2009 Volvo D13 Won’t start unless I wiggle this wire

(Repost)
Hey guys so my problem right now is that my truck doesn’t start sometimes and when it doesn’t I open the hood and touch this “one” very specific wire coming from the firewall and bam It starts no problem. (Give a little wiggle)

Some details to note is when it doesn’t want to start there’s a certain solenoid click that I don’t hear
But when I touch that wire I here that specific solenoid clicking I can get you guys a video here shortly.

My guess is either corrosion or a short. I re-soldered the wire because i thought is was loose and it looked like someone worked on it before but it didn’t solve the problem.
Here’s is a picture of me pointing at it.
Any diagrams would help so I can test which wire it is thank you.

 

Here is a link to the video of what I mean by the solenoid clicks and sorry if you can’t hear it there’s an interstate where I’m at. Hopefully one of you techs have an idea of what it might be and which wire it is.

 

Everything seems to still be OEM except those two wires I re-soldered.

 

So after doing some research and looking up diagrams. My guess is this wire has some sort of break or corrosion.

It could either be the 12v supply wire that engages the relay to complete the circuit to the signal wire to the solenoid ground,
Or the signal wire itself from the relay to solenoid ground.

I will test the wire with a multimeter to confirm which wire it is, after I confirm that I will try to see if I can rewire/Hotwire it with brand new wire from the MCFC Connector to whatever terminal. and see if the problem persists. I will do it when the truck doesn’t want to start or disconnect the wire so I have 100% confirmation.

And I promise this won’t look like a hack job

 

Here’s the diagram I looked at pretty straight forward hopefully. The hard part is finding which wire is which on the MCFC connector.

 

Thanks for the Input! I will definitely try that when it doesn’t want to start!

It only doesn’t want to start up when I let it sit for a few minutes. But if I shut the truck off and turn it back on right away it starts no problem. Probably from the vibrations.