It's the ground lug that is bolted to the body of the car.I had this transmission malfunction on my 2011 Fiesta (won't up-shift correctly) after replacing the battery last winter and finally had the car serviced the other day by my local private repair shop. I tried various tricks to get the controller to reprogram including disconnecting the battery again for a while and reconnecting, putting miles on the car, driving it through a series of acceleration runs at graduated intensity so it would "re-learn" proper shifting and nothing worked. I did find that the car can be forced to up-shift by putting the shift lever in neutral for a few seconds and waiting for the revs to drop, then back to drive. Still, it was a pain to have to do that every time I slowed enough to drop to a low gear. My service tech read the codes and cleared them, then told me I'd have to go to Ford for help. Anyway, the morning after he returned my car to my driveway I went out and started up and lo and behold, not only were the annoying error messages gone (which I expected since he cleared the codes) but the car drove and shifted normally again. Whether this will last once I've gone the required miles for the computer to register new faults again, I don't know.
If I were the suspicious type, I'd wonder if Ford did this on purpose to get people to see a dealer even though all they really need to do is clear the codes and the problem will disappear. If all else fails, get somebody at the local auto parts store to loan you a code reader and clear any codes. It just might be all you need.
Remove the bolt, Sand off the paint and replace.
Clear out the codes.
Had the exact same thing as you.....