Hi Phil, I have a 2018 Silverado LT and I've just installed passenger side DL3 mirror with the 84125566 harness that comes with. I founded out after all that mirror adjust functions were not active so I've compare the original wiring harness and put wires that were missing to get the adjust but still not working... Nothing has change in the driver side door so the adjust signal pins should be still working right?
What I've done so far:
I've took wires on cavities 9-10 from the mirror connector of 84125566 harness(I found out that those wires are the ones to make the mirror adjustment) and feed them from cavities 36-38 of the door connector.
I also wanted that my cargo lamp activate the mirror puddle light so I manage to put a pin in cavity 9 with a diode and feed cavity 3, at least this is working fine ;)
BTW it's really a pain in the ass trying to remove pins in the door connector.
Once I will find a way to activate passenger side mirror adjustment, I will do driver side, the mirror switch with fold button is already ordered... Please let me know if I'm in the right way
Thanks!
Thomas