Trailer lights not working - tested plug and checked 3 30a fuses in engine bay

[caskew13]

Howdy - just got my 2015 SR5 a few weeks ago. Today, I went to plug in my drift boat trailer for a trip tomorrow, and I get zero trailer lights.

I plugged the trailer 4pin straight into the truck 4pin. I didn’t mess with any 7 to 4 adapter.

I got a circuit tester to check the truck socket, and I get red lights on it when testing for everything- blinkers, brakes, and the running lights.

The 3 30a towing fuses look perfect in the engine bay. I didn’t see anything else on the inside panel related to towing.

Is there a square fuse or other item Im passing over? I checked the connection under the truck directly to the socket too, but it seemed okay.

Trailer lights worked fine on my 2000 4runner a month ago.

I’m terrible with wiring and appreciate any help. I have a multi meter but don’t honestly know what to do with it for this issue. Not even sure what shop I could take it to to check something like this.

I hate to run the trailer with no lights and chance a ticket, but I have to take clients tomorrow and chance it.

 

[jonz]

Stupid question, but was trailer hooked to the truck when you tested? If not your trailer doesn’t have a ground path back to the truck.

 

[CavPro]

On a trailer, always start with the ground.

 

[caskew13]

So, yesterday morning, once I got to the ramp, everything was working as usual on the trailer. I've got no clue. When I left the house, I had no trailer lights, and when I got to the ramp 2 hours later, I had lights. :der: