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

0

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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How to Troubleshoot Trailer Running Circuit on 2005 Toyota 4Runner

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