Well, by coincidence or not, my Mom was in town for a week and loves to grab a tailgate and manhandle it, likely a leftover habit from the good old days and the '86 Plymouth Voyageur we had growing up.... then the power feature on the tailgate stops working.
Every fix I came across is basically: My tailgate is broken - Ok, push the button in the glovebox and try again. - Oh that worked, thanks.
To be clear about the symptoms, the motor that grabs the door and pulls it tight still worked, but the one that raises and lowers the door was not doing anything. I'd get the 3 beeps sometimes, but that's it.
So I decided to dig in.
Here's what I'm looking at. Problem must be in here.
So you can see I pulled down the headliner. I just got a finger in there by the actuator arm and pulled at it. It's held up towards the right side by a couple of these.
Now when I looked in the mechanism, I saw that the arm that the motor drives had popped off of the pin for the door side arm.
Looking at this pic you can just barely see that there's a small bushing inside the end of the motor side arm. That was actually still sitting on the pin when I first got in there but I took it and pressed it into the motor side arm with a pair of pliers. Also note that the pin has a small groove at the top, you'll need to get a C-clip in there.
For reference, the C-clip I used.
I had to push the motor arm back into the mechanism a bit to make room to get it back onto the pin, then pull the door down a bit and massage it to get the arm on there. Then pop the C-clip on. Surprisingly, I managed to get it on first try.
Lubed up the struts on the tailgate for easy operation, opened and closed it a couple times manually ( I read somewhere this resets the system. Who knows. ) And viola! It works just like it's supposed to.
This is the motor arm on the pin.
Tools I used: I had to use the coathanger to pull the motor arm out from the very back of the mechanism when I started, it had pulled all the way in as if to close the door. Pliers to seat the bushing in the arm, and to seat the arm on the pin. Screwdriver to push the C-clip on.
I hope this helps someone. I was motivated by fear of dealership service departments.