Tailgate locks but won't unlock
 

I bought a used 2015 F150 Screw and the tailgate lock won't work.

I've since replaced the tailgate actuator with no luck. Thinking that its an electrical / ground issue I found that when I grounded the ground (see pic) wire that it locks but won't unlock. So now its stuck in the lock position.

https://cimg6.ibsrv.net/gimg/www.f15...d16b071199.jpg

New tailgate actuator.


Anyone else have any ideas on what I can try next? My next guess that the hotwire sends a different amount of power for unlock or lock so I might try and tap into an unlock / lock wire closer to the cab.

Thanks!

Looking at the wiring diagram, the polarity of the two wires gets reversed. So remove your ground wire, you have an open in one of those wires. I can't tell which wire you have connected to ground. If you hit the lock button the gray/brown is hot, the brown/green wire is ground, when you unlock its the opposite. Did you check the plug right under the bumper? The other end is under the hood of the truck on top of the drivers side fender wheel. Pin 1 would be the brown/green and pin 34 is the gray/brown.

If I recall correctly, polarity is reversed to unlock the tailgate.

(Also note this a security vulnerability with the trucks, I could easily make a device that plugs into the tailgate connector to unlock the tailgate and get access to the bed of these vehicles).

I did check the plug right under the bumper and everything looks ok. I'll remove the ground wire and take a look at the driver side fender wheel. Thanks for the input! I'll report my findings asap.

Thats why I couldn't get a good read with my multimeter... that explains why I could get a read on either lock or unlock but not the other way... Thanks!

I would test underneath the truck, the wire maybe open going up to the tailgate. One lead to ground and test each wire first, then at least you know which way to go.

If someone is breaking in, doesn't make a difference how its locked, they will get in.

Found the issue thanks to Gordy49913s recommendation on checking under the hood. The harness in the pic below wasn't on snug enough and it didn't lock together as it should since one of the plastic pieces was off the hinge. A quick 5 minute fix and everything worked on the tailgate including the backup lights. Thanks everyone!

https://cimg8.ibsrv.net/gimg/www.f15...b16559ce06.jpg

Driver side electrical harnesses.

Thanks for letting anyone that reads this.