2016 F150 King Ranch 5.0 4x4, I have been fighting the rear park aid randomly not working along with the tailgate button not opening the tailgate. I found out this vehicle had and exteded warranty and I took it in to the Ford dealer. They installed the unattended tailgate opening wire bypass kit under the back by the spare tire and made the tailgate work again with the button on the tailgate. I was hoping this would fix the intermittent park aid issue but they said there was a bad sensor so I was excited about that. Got the pickup back, replaced the passenger side outer sensor myself and everything was working great. I found the canopy wiring that went into the cab and fixed the rear brake light on the canopy that wasn't working as well, I had posted about that trying to get help as well. When who ever had it done put the lower dash parts back on the wire was pinched and broken. The wire was run to the back side of the trailer brake controller panel on the dash. I fixed that wire and the brake light on the canopy works fine now. So everything was going great and then intermittent issues again with the park aid started with the bad weather. The Park aid error is what I get on the instrument cluster in the cab, I get a big square screen with a gray pickup with a small red circle with an exclamation point in the circle on the sync display while I am driving and when I put it in reverse. Sometimes it will just start working again fine and then all of a sudden it starts acting up again. I have been looking at everything I can find online about it and found where you can test the sensors with a stethoscope. This last couple weeks it has only worked 1 time so I got the stethoscope out and found one of the sensors is not clicking, drivers side outer at this point in time. I have a brand new sensor, I bought 2 when I had to replace the other one that was bad, I installed it and same thing, didn't work. I then swapped the sensor for another one and the sensor that wasn't clicking clicked just fine in another slot. I think it is a wiring issue at this point. I took all the connectors apart at the back of the vehicle, they are all perfect, I blew them out with air, I applied some of the Ford connector grease to all of them. Removed all the wiring connectors on the sensors, cleaned and applied the grease as well. I also checked and blew out the trailer wiring connections on the bumper. I removed the ground points on the frame in the back as well, sanded everything, cleaned the bolts, applied the grease and put them back together. I do tow once and a while and all the associated trailer wiring is working fine as well. Still doesn't work and no clicking from the drivers side sensor.

If anyone has any more info to help that would be great. I can see where the wires go to the main connector in the back by the spare tire but I have no idea where the wires go from there up to the front of the vehicle. If someone has a wire diagram or what you should read from the pins of the backup sensor wiring that would help. I would also like to unplug the large connector and test to see that the wire from the large connector to the sensor is ok. Maybe there is a connection up under the hood, cab or along the way under the vehicle I can check, disconnect and re-connect that would help. I am going to go under and try and find some more grounds I saw on Youtube up at the front of the vehicle, remove them and clean them as well. I hope there is just another connector somewhere that I can inspect, clean and grease up to keep the water out to get this fixed once and for all. Or possibly a wire that is bare or almost broken or something. It is kind of strange when your driving it pops up the pickup with red circle on the sync screen.