Trailer Harness on 1999 Toyota 4Runner Does Not Work
Updated 12/07/2025 | Published 01/29/2014
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Question:
I connected the wiring plug male from my new trailer to the harness connection on my Toyota 4 runner female, but nothing happened. I can see the wiring going into the rear of my 4 runner from my trailer hitch. This is the first time Ive tried using the trailer light connector. I looked in the Haynes Manual for an electrical schematic showing where the trailer harness is located, but it was not listed. I also checked the owners manual and nothing there either. I went to Auto Zone to see if they sold a relay or fuse and the salesperson looked it up and said there is a relay for the trailer connection, but they dont sell it. I did not see any mention of a trailer fuse or relay in the fuse box under the hood nor the fuse box located under the steering wheel. Can someone help me? Thanks
asked by: Joseph M
Expert Reply:
Since this is the first time you have used the connector on your 4Runner, if it has been awhile since it was installed or if it is factory then there can be some corrosion build up inside the connector preventing it from working. This happened to a friend of mine recently. Scraping out the corrosion will help. Also make sure the main ground is connected to a clean and corrosion free bare metal surface.
If that does not help then use a circuit tester such as # PTW2991 to test the vehicle side connector while someone sits in the 4Runner and runs through the lighting functions. If the 4-Way shows no power then check the wires leading into the converter box. If they have power going in the box but not coming out then something is wrong with the converter and the wiring harness will need to be replaced.
If there is no power on the input side of the converter then there is something wrong with the vehicle wiring. But if this were the case the tail lights on the vehicle also would not work.
If you have factory wiring then use the vehicle owners manual to find the locations of any fuses/relays associated with the tow package wiring. If there is nothing in the manual for this a Toyota technician should be able to assist you.
If you wanted to add a different wiring harness I recommend # 118341. It just plugs in line with the vehicle tail lights.
Product Page this Question was Asked From
Curt Tail Light Converter with 4-Way Flat Trailer Connector
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Vehicle End Connector
- Powered Converter
- Universal Fit
- 4 Flat
- Plug and Lead
- Splice-In
- CURT
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on Custom Fit Vehicle Wiring
Mike
12/5/2025
WHERE IS THE CONVERTER?