Best Option For Replacing OEM 4-Flat On 2015 Toyota Highlander
Updated 08/17/2026 | Published 05/24/2025
Question:
I have a 2015 Toyota Highlander with the factory tow package. We dont tow often, and when we do it is just a small trailer. The vehicle has a 4-pin flat connector. Today when I went to connect the trailer, the metal pin sleeve for the right signal/green wire connector on the vehicle side had dissolved into a green/blue soup. No metal left. Im not sure what happened, as it was capped when not in use, but I live in WI and winter salt corrosion is always an issue. After replacing the bad connector on the vehicle side, I put a tester on the new connector. The right signal is still not working properly. The LED for the right signal on the tester will flicker and blink lightly, but not like the properly working left signal readout. Additional test with a multi-meter confirmed it isnt getting proper voltage. My question is whether it is likely the converter module was damaged, and if so, can I replace it with a more economical 3rd party converter rather than the expensive and much more difficult to find factory module. If so, do you sell any plug and play solutions? The factory part is a DENSO LA061800-1330. Thank you,
asked by: Shane D
(click to enlarge)
Expert Reply:
Hello Shane, thanks for reaching out. That does sound like a bad converter module to me. It is a fairly common issue unfortunately. We do not have a direct replacement for the OEM module, but we do have an aftermarket option. For that, I recommend the following:
- Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector # C56217
This will bypass/replace the factory wiring. Take a look at the install video I linked for you below.
Hit the reply button and let me know if there is anything else I can do to help.
(click to enlarge)
Shane
8/17/2026
This ended up being a simple and effective solution. Basically just unlatch the factory converter module and drop the Curt #C56217 in instead. The included instructions were completely accurate and the repair took maybe 15 minutes, most of which was unloading stuff from the car to get to the connector. If you have a factory converter that has gone bad, this will fix it quickly.
Product Page this Question was Asked From
Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Vehicle End Connector
- Powered Converter
- No Tow Package
- 4 Flat
- Plug and Lead
- Plug-In
- Hidden
- CURT
more information >
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Jesse M.
9/12/2025
Hey Shane, did the Curt T-Connector wiring harness work out for your Highlander? I'm curious to know if it solved the issue, as it could help others facing similar problems with their trailer connections.