Trailer hitch wiring yaris 2012

[Strider199]

I was going to post this in the electrical section but this is a problem with a new 2012 Yaris.

This past week end I used my multi-meter to find which wire goes to what in the left rear tail light connector after I removed it from the socket.
I was happy to find, running light, brake light, and left turn signal. I used the fast splice connectors to attach the wires from the 5 to 4 wire converter. I than found the right turn signal in the right rear tail light plug. I was done. I used the multi-meter to check the power out put on the plug which goes to the trailer. Everything seemed fine. As a note, the ground is fastened under the screw to the tail light which seems like a strong ground.
I hooked up the boat trailer harness and turned on my various lights.

Not a glimmer. After disconnecting the car from the boat, I got my 12 volt battery out and using a couple of leads, I tried each wire plug on the trailer. Each test on the trailer lights was successful. I also re-tested the car plug and found only 4-5 volts coming from the taillight.
After the key had been out of the ignition for 5 minutes, the voltage was back to 12 volts on all plug connects in the car.
After double checking which wire gets power from what circuit and finding every plug connection was ok, I tried again to power up the trailer lights same result.
Back to the drawing board.