Troubleshooting Trailer Wiring of 2009 Toyota Sienna with No Stop/Turn Circuits

Updated 07/24/2020 | Published 07/23/2020

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(180)

$42.78

T-One Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(380)

$47.25

Question:

Hi, I have a Curt 55580 T-Connector harness attached to a Curt 57674 7-way plug. Today I hooked up my trailer and found I had running lights but no brake or turn signals. With the trailer disconnected the indicators on the 7-way look good until I plug in the trailer. Only the running lights indicator stays lit. I am using a multimeter not a circuit tester. When checking the voltage at the 4-way flat connector the brown wire is a good solid 12v but the voltage for the yellow and green wires the is jumping around and is usually pretty low. I am measuring across the white pin to the other three brown, green and yellow on the 4-way connector. Can you tell me if the voltage on the green and yellow wires should be just on-off, 0v and 12v as the lights blink on and off or is it normal to see highly fluctuating voltage?

asked by: Gene H

Expert Reply:

It sounds like a converter box issue on your setup. Can you test for voltage feeding into the box and coming out of the box? I'd be willing to bet you'll find it's going into the box fine but not coming out which means it has an internal short and would need to be replaced.

We've found that the most reliable trailer wiring brand is Tekonsha so I would recommend replacing what you have with the part # 118304.

expert reply by: Jameson C