Troubleshooting Trailer Running Lamps Not Working After Replacing 7-Way Trailer Connector

Question

Question:

I have a Toyota Sienna 2009. My 7-Way Blade Vehicle End was too low on the vehicle so it scrapped up on low speed bumps. I had an Expert Shop replace the 7-Way and place it higher. After replacement the Expert said that the signal and break connect works but due to the original wiring to the 7-Way had been scrapped open it causes a short or blown a fuse so the Running Lights do not work and they believe its the fuse in the vehicle. They said they are not vehicle mechanics so I should take it to an automotive repair or dealer. After thinking about it I looked into my vehicle Manuel and located the three fuse boxes and since I do not know which fuse its connected to it I pulled out each removable fuse not including permeant ones to look it over. They all looked good. I even placed a 7-Way to 4-Way Adapter with LED light to confirm that the Running Light does not work. I traced the wires from the plug to the Break Control Module and the connection to the Battery. It all looks goods. I wonder, if the Running Light brown wire on the connector is not working then would that mean my vehicles Parking Light should not work too? Could a wiring short cause one of the two Circuit In-Line Breaker not work properly causing this problems as well? The only other explanation I can think of is that the new 7-Way Connector they install is defective. What could I do?

asked by: Rafael

1

Helpful Expert Reply:

To determine if the problem lies in the vehicle or the trailer wiring, use a circuit tester like # PTW2993 on the pin in the 11:00 position on your 7-way while the vehicle headlights are on. If the pin shows voltage on it, the problem exists somewhere in the trailer wiring. If you don't get any power on that pin, the issue is with the wiring on the vehicle.

If the running lamps on the vehicle aren't working, check fuse # 17 in the fuse box under the driver's side dashboard. If they are working, the problem is most likely that your taillight converter is blown.

Your 7-way was probably connected to a 4-pole to 7-way adapter like # 37185, with a taillight converter providing the lighting circuits for the trailer. The short in the trailer wiring likely caused the converter to short out. Trace the wiring leading from the rear of your 7-way, looking for a brown green and yellow wire that leads to a small black box. On the input side, there should be a brown, green and yellow wire. The brown wire should carry the running light circuit. Use the tester on the brown wire on the input side. If the brown wire on the input side shows a signal on it, but not the output side after the converter box, the converter has been fried and should be replaced. I'd recommend using the Tow Ready Taillight Converter, part # 118304.

I'll also link you to our Trailer Wiring and our Wiring Troubleshooting FAQ.

expert reply by: Mike L

1