So I did some more digging around in the lift gate. I took the lock completely out:
I made sure all the movable parts on it could indeed move and weren't "frozen" from corrosion. I definitely thought it would be a corrosion problem at first because look at my posts:
However, since the lock seemed fine, I moved on to the wiring:
I'm not the best at reading schematics but I figured a trusty meter would help me make sure I was getting power to the lock. Sure enough, I was:
I was getting around 8 volts to the gray wire leading into the lock on the two-wire harness when I hit the lock button on the keyfob. I wasn't able to get any readings off the three wire harness leading into the lock...and from what I can tell, those wires are just for the "ajar" and "open" sensor so I didn't really need to worry about those.
Even though I had already checked the wires leading thru the boot near the top of the liftgate glass, I decided to take another peak. Lo and behold, I find a crack on the plastic insulation on the fat orange (HOT!) wire and the fat black ground wire. The Orange wire still was hot surprisingly. I figure something like that, if it actually would have ground out, would have popped a fuse or something...but nope, it was still hot!
I could tell something was up right when I pulled the lower portion of the boot off because it had a bad electrical tape job over some wires. Definitely not from the factory:
So I pulled back the electrical tape and there it was! Hot orange wire right next to the ground wire:
So I cut the wires and tossed in butt connectors and did a good job with the electrical tape and sealed everything back up.
Now my question to you is what do you think my problem is since I have 8volts going to the lock but the lock isn't functioning. It was sending the 8 volts even before I found the wiring issue, so that makes things a bit strange. Do you think the wires shorted something out in the LGM causing it to malfunction? I don't think that is the case because it is properly sending out the 8volts to the lock thru that gray wire...the lock just doesn't do anything.
I'm thinking it's the lock but let me know what you think now that I have all the information...