Loss of electrical connection to trailer

Tinnitus

Last weekend, my wife and I went camping with our 2020 T@B 400. About an hour into the ride home, a warning sound and message on the dashboard of my 2020 Tundra indicated a loss of connection with the trailer and no trailer brakes. 

I pulled over and found the cable securely installed at the truck. It hadn't come loose at all. I unplugged it, waited a few seconds, plugged it back in. Connection reestablished. The rest of the ride home was normal, where I unplugged the trailer for the night. 

The next morning, I plugged it back in, started to reverse out of the driveway and the warning happened again. I unplugged, replugged, got about a block away and the same thing happened. One more "reboot" and I was able to get to the storage facility with the trailer brakes working. 

Now: none of this happened on the drive OUT to the camp ground early on the weekend. And it did not happen at all on the drive in December from Las Vegas to East Texas (where we are now), with the same truck, or during all the camping we'd done in Utah during the previous year and a half. 

So, what's going on? Could there be some corrosion on the male and female connectors? Could there be a fault on a fabulously expensive circuit board in the truck, for which there will be no replacements available for rest of the calendar year? 

Any ideas?

Mouseketab

I would try cleaning the connections on the 7-pin on both sides and coat with dialectric grease.

Horigan

I would first spray electronic contact cleaner on both receptacles and connect and disconnect multiple times to clean the contacts.  Then I would maintain it with CorrosionX, or equivalent, to prevent further corrosion.  I would also look at the tangs in the female connector and maybe bend them in a little bit so they get better contact to the mail pins on the TV.  If it still keeps happening I would look at the junction box under the tub where the tow wiring connects to confirm it is sealed and there is no corrosion inside.  If there is, clean the connections and reseal.  Note there is 12V from the battery in that junction box.

Grumpy_G

The truck detects the presence (or absence) of trailer brakes by measuring resistance to ground on the brake control output. The actual connector is the obvious place to start but it could also be anywhere else in the wiring to the brakes *and* the ground connection from the trailer back to the truck. The latter can be tricky because even if the ground wiring is bad the connection is made through the trailer hitch which in turn can be intermittent because of the moving parts. 

Tinnitus

I guess my suspicions are leaning toward corrosion on pins, if only because the trailer/truck combo spent so much time in Nevada/Utah (normally dry and still going through a multi-year draught on top of that), to the wetter, more humid climate of the Brazos Valley. Electric contact cleaner and CorrosionX seems like the best place to start. Thanks, guys.

tabiphile

@Grumpy_G has laid it out for you. 
These connectors are designed to have an interference fit. They scrape together to make a connection. A Dialectric grease or CorrosionX is not designed to improve the electrical connection. In fact, they may degrade it.
You should clean the connectors to remove any contaminating greases and inspect each pin to make sure that they are properly seated. 
A cleaner will remove grease that might be degrading the connections. 
More likely is that you have a poorly crimped connector that is giving an intermittent connection. If you have a connector tester, plug it in and see what you learn. Next, using a pin removal tool, you might remove the connectors from the housing to check the crimps.
If you are not comfortable with that, a trailer shop can probably get you sorted quickly. The pcb in the truck is an unlikely root cause. 

Tinnitus

Today I bought a can of CRC quick drying electronic cleaner and the directions state: "Do not apply while equipment is energized."

I'm not sure what that means. Is the truck-end connector "energized" (from the battery) when the trailer-end connector is not connected? 

Does it mean I should pull a fuse before I apply the cleaner? 

Denny16

Turning the tuck off and make sure the truck driving lights are off, should disconnect any power going to the 7-pin, but you should test the +12VDC charging lead with a meter or tester first.  CRC can be flammable, which is why you want power off before using the stuff.

I agree with Tabiphile, that you more likely have an interment connection caused by poorly crimped connector on the TaB connection bus where the 7-pin cable is connected on the front of the trailer, or on the truck 7-pin connector.  I would check the truck first, then the TaB.
 Cheers