Trailer hitch wiring yaris 2012

[Strider199]

So after work I tried to hook up the converter again.

I spliced in the running lights right to a running light bulb which I checked with my tester. Plugged in the trailer and the running lights where on.
I then spliced into the left signal light and tried that. Worked great.
I then spliced into the right turn signal and it worked great.
I then spliced into the brake wire at the bulb and had my son push the brake pedal. It worked great.
Thought I was all set but then, I put on the 4 ways. The rear trailer lights flashed but they were dim. I stopped that and turned on the running lights again, nothing. I tried the left signal, both signal lights flashed dim. I tried the brakes, nothing.
I SHUT IT DOWN.
Tomorrow I will pick up a powered trailer light converter and see how that works.
Why are they making the wiring in almost every car so frustrating these days?????????