I bought a 2011 a couple years ago. Same issue with the rear driver door lock not working. Just never got around to replacing it.
Then about 6 months ago, the speaker in that door stopped working. OEM Radio was starting to go out at the same time so I figured they were related. Swapped radio and the speakers (gotta have tunes) to no avail. At this point, I know it’s a wiring issue (at least for the speaker) that I would address when convenient. Still had sound from the other speakers.
Then about a week ago, same door, I started to get “left rear door open” errors on the dash. OK. Last straw especially because it was intermittent.
In playing with the door, I could squeeze the ribbed rubber tub (probably not the best technical term) and get the error to go off and on. Now I know the wiring issue (at least for the door open error) is somewhere in the wiring cluster that runs from the B Pillar into the door.
So, I removed the door panel, peeled back the vinyl backing and removed the wiring cluster. After undoing the tape nearest the main harness, I found 4 wires that had broken. I’m guessing age of the vehicle and from opening/closing the door. Just like breaking metal by bending it over and over.
I spliced those 4 wires and now, no more error, speaker works and the door locks/unlocks every time I click the phob or door button.
I know that’s a little long winded, but hopefully it helps. If yours ends up having the same issue and you don’t want to splice any wires, I believe the part number is 14632B from parts.ford.com.
