Tow adapter is wobbly, losing connection for lights and brakes.

Last week I was towing my horse trailer, everything was working fine... until I got a triangle shaped caution sign flashing at me on the display, stating "error" & then the green trailer connection display began to flicker, like a short or something. I pulled over and checked the plug, everything was the same as I started out with, plugged in secure. I unplugged it and plugged it back in again and it worked fine until I hit a bump and it revealed again no trailer on the display, no trailer brakes but the manuals worked. The horse trailer tested fine with other vehicles. I hooked up the 2016 Tundra again and noticed the adapter is wobbly & by moving it it seems to cause a disconnect as the trailer lights go off and on. It's does not seem to be the trailer since it works fine hooked up to the older 2006 Tundra no issue with turn signals, lights or brakes. I took the 2016 into the Toyota Dealership for a second diagnosis, Tuesday will be my third trip back. Now it's out of warranty but was during the first diagnosis. So far 1/2 tank of gas to and from and 2 full days spent with the dealer now looking at a third day. One employee suggested anchoring any slack in the tow cable. But looking, there wasn't too much slack to secure. it's still doing the same thing, behaving like a short when the truck adapter is moved or jiggled as it's being hooked up...it works intermittently and I can't tow a horse til it's fixed, I bought the truck for the sole purpose of towing the horse trailer. The adapter on the truck is fastened per factory to the truck on only one side of the adapter allowing it to wobble, why wouldn't it be screwed in and secure on both sides to hold it tight. Anyone else have these issues? any suggestions? the first time I took it in the service dept cleaned out some debris & it seemed to work fine for a while but doing the same exact thing. The service dept says it's got current and working fine.

 

The adapter on my Tacoma sucked until one day I ripped it off going through a creek. I put an aftermarket one on and it worked much better. Of course I had to cut the factory wires.

 

Maybe it’s possible the pins aren’t making a tight connection. Either the ones on the truck are too small for the female end of the trailer harness, or, the harness is stretched out matching your old truck. Maybe it’s possible to take a pick and collapse the female connectors inside of the harness.

 

Was the dealership specific about the "debris" that they cleaned out? If it was green corrosion it's very possible that it's also behind the spades. If there's corrosion behind them it can cause current to jump spades which can cause a dead short especially if current can jump across the ground spade. If you unplug the harness from the back of the plug you can look at the pins and if there is corrosion it may show itself.