Troubleshooting 2007 Toyota Sienna Trailer Wiring Where LED Circuit Tester Shows Odd Results  

I have been vexed by trailer lighting problems on my 2007 Toyota Sienna minivan which uses a wiring converter to output into a 4-pin standard flat connector. Mechanic who did the install assured me that he followed the Tekonsha instructions when making connections and found a suitable ground on the vehicle. When I plug a 4-pin trailer light tester into the vehicle 4-pin connector, the testers lights indicate the same incorrect lighting patterns that Im seeing on the trailer. 3 LEDs on the tester lights are Tail, Left and Right in order of left-to-right. Left and Right are intended to illuminate together with brakes. See attached picture of the light tester. This is the second unit that Ive tried and both have given me the same incorrect lighting patterns. I believe the first one was a Curt I bought from eTrailer and the second a Tekonsha from a local trailer dealership in my town. Here are the lighting results, first group is without running lights and second group is with running lights. With running lights not on: Left signal=Left and Right flashing together on tester Right signal=Tail LED flashing on tester likely both turn lights on trailer Hazard=All three LEDs flashing together on tester Brake=Only Left LED is lit on tester With running lights on: Running lights=Right LED lit steady on tester Hazard=Tail and Left LED flash together alternating with Right LED on tester Right Signal=Tail LED flashing and Right LED lit steady on tester Left Signal=Left and Right LEDs to flash alternating on tester Brake=Left and Right LEDs are lit steady on tester expected result

asked by: Brad S