How to Troubleshoot Trailer Running Circuit on 2005 Toyota 4Runner

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Question:

I have an 05 4Runner with factory tow pkg w/ the 7 round plug. I have power for brakes, turn signals brn and re wires, but no power for tail lights. I tap into the wires on the vehicle side but no power there either. Im not sure which wire should be hot for tail lights - blue or yellow? Help! Thanks.

asked by: Rick

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Expert Reply:

I do not have any specific information about what color wire feeds the running light circuit to your OEM 7-way on your 2005 4Runner. Vehicle manufacturers have been known to vary wire color within the same model year, so wiring by color does not always work.

If you can access the rear of the connector, and find the terminals where the individual wires attach, the wire that feeds the pin in the 1:00 position will be the running light circuit. I have linked you to our Wiring FAQ article that shows how the 7-way should be wired.

Once you find this wire, and if your testing indicates you have no power on this circuit while the running lights are on, you are probably dealing with a blown fuse. The fuses that protect the towing circuits are typically located in a fuse box located under the hood. In my research, I was unable to find the specific fuse location you are looking for, but the box should have a legend on the lid. You can also check your owners manual for the specific fuse location. Once you locate and replace the fuse, before plugging in your trailer you will need to locate the short on the trailer that caused the fuse to blow. Trace the running light circuit on the trailer, looking for pinched or broken wires. Look for any worn or cracked wire insulation that would allow the copper conductor to short out on the trailer frame. Make sure that the connector on the vehicle and on the trailer is in good repair and not corroded.

If you do not track down the problem in the trailer wiring, you will continue to blow fuses.

If you cannot locate the fuse, or if the fuse is not blown, it might be easier to simply bypass the OEM tow package and install the # 119178KIT. The inputs would splice into the individual lighting circuits that you would locate using the circuit tester included in the kit. You could plug the 4-way provided by the harness into an adapter like # 37185.

The brake output and 12 volt power supply circuits already in place can be removed from the OEM 7-way and attached to the blue and black wire on the adapter.

The # 119413 is for a 2001-2007 Highlander, and would not work with your 4Runner.

expert reply by: Mike L

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Answer 1

There is no way to reuse the same bolt holes that held on the OEM 7-way with the new Hopkins Plug-In Simple Vehicle Wiring Harness for Factory Tow Package #HM43374 on your 2008 Toyota 4Runner. You can drill new holes if you wish to reuse the factory…

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Answer 2

We can definitely help set you up with a tow package for your 2024 Kia Telluride. The main components you will need are a hitch, 7-way wiring harness, and a brake controller. You will need a good ball mount too, but it sounds like you have that…

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Answer 3

If your Highlander has an active tow package plug located in the driver's side rear of the cargo area under the floor (see linked instructions for part #C56107 to see where plug is located and how to access it) your Highlander has the tow…

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Answer 4

Based on the troubleshooting you've done so far you have a shorted out converter box of your trailer wiring harness. The only solution in this scenario is a new harness. For that the Tekonsha brand like part #118413 is our most reliable option so…

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Answer 5

It sounds like your truck will use a 7-way harness like Hopkins #40167 which uses connectors like what you describe. Please refer to the linked photo that shows those connectors. This includes a 7-way socket that plugs into the included round U.S.…

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Answer 6

The correct trailer wiring harness for your Highlander will depend on whether or not it is equipped with the tow package and the lighting set-up of the trailer you will be towing. If your Highlander has the tow package, and you will be towing a…

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Answer 7

If you have no power to the trailer wiring harness, the fuse panel is located in the engine compartment. I have attached a drawing that shows where the fuse panels are located on a 2006 Highlander. Per the second attached drawing the fuse for trailer…

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Answer 8

I would recommend hitting the lock with some WD40 to try and get the lock core to release. Use the straw that comes with it to direct the lube into the core as much as possible. You may have to let it soak for a few minutes. Working the key in and…

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Answer 9

if your 2003 Toyota Highlander has a tow package plug located in the driver's side rear cargo area under the floor (see instructions for installing Item #118413 on where to look) then your Highlander has the tow package. If you find a plug, use a…

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How to Troubleshoot Trailer Running Circuit on 2005 Toyota 4Runner

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