Do the trailer lights work when using the flashers? If so they are not the problem. Even though they are different circuits the wiring beyond that would be the same. If you want disconnect the trailer lights and if they now work and they will blink real fast then they are the the issue but I don't think it will make a difference. I've never had an issue with any on a Toyota but I would assume there are two flashers, one for the emergancy and one for the turn signal so if you may need to find the second one. I just looked at a Tundra here at work and it has two.