Does Curt Trailer Wiring Harness Really Fit 2026 Toyota Grand Highlander without Tow Package

Updated 02/02/2026 | Published 01/20/2026

Question:

I recently purchased a 2026 Grand Highlander and wish to install an after market hitch and harness. I have read that there are lot of issues that with the Curt 56524 c56RV the trailer turn signals switch sides while the brakes applied. One of your explanations is that the Toyota OEM module PT725-48241 needs to be installed. Does this not make the Curt 56524 redundant as only one module can be installed? Is the Curt module design defective? Is it not deceiving to continue to suggest that the Curt module/harness is plug and play?

asked by: Fred B

Expert Reply:

Hey Fred, you would need the Toyota harness part # PT725-48241 but this is not a complete trailer wiring harness. This is basically an intermediate harness that the Curt # C55245 needs if the Grand Highlander does not have the OEM tow package. I would say it's a little confusing to say this fits all Grand Highlanders but that is why we state it only fits the versions that have the tow package. I think the most ideal solution would be for Curt to include the Toyota harness but it's most likely something only Toyota can offer.

expert reply by: Jameson C

Don

1/22/2026

I totally agree with Hal’s comment posted on 8/3/25. I installed this kit on my 2024 Grand Highlander when it was new. It was easier to install the control box as he states. I also installed a wiring plug purchased previously and it was wired differently. Definitely use the one that comes in the package. Haven’t had any issues with this wiring harness since installation and swapping between two different trailers.

Jameson C.

1/22/2026

@Don great feedback thank you !

Steve C.

1/22/2026

Fred B, You are correct. The turn signal lights do switch sides when the brakes are applied with the Curt converter. I ran into this problem with my 2025 Grand Highlander. Toyota makes their own module. Part #PT725-48241is what I installed. I paid around $90 back in June of 2025. Detailed instructions were included. Assuming that the 2025 and 2026 Grand Highlanders are similar, the module is mounted behind the driver's side, 3rd row cup holder panel. It plugs into a multi-pin connector and then mounted with 2 small 10mm bolts that are provided. It is relatively easy to install. This device provides connectivity to a 4-pin connector under the driver's side rear bumper where you would then connect a 4-pin trailer harness that you also need. I believe Curt part #C55245 is what you need. These are the only two items you need to add turn signal and brake lights to your trailer. You do not need the Curt module (Curt 56524 c56RV). Hope this helps.

Jameson C.

1/22/2026

@SteveC Awesome feedback! Is the other harness needed the part # C55245?

Steve C.

1/22/2026

@JamesonC Yes. Part #55245 connects/adapts Toyota's square 4-pin connector under the driver's side rear bumper to a flat 4-pin trailer connector. As the photos for the part shows, there is more than enough wire to get to the vehicle hitch.

Jameson C.

1/22/2026

@SteveC good to know! I will edit my answer page to show this.

See All (4) Replies to Steve C. ∨

Cough

1/24/2026

I dont understand then why etrailers sell the Tekonshah T-One TK99FR which is listed specifically as compatible with the Grand Highlander without Factory Tow package for $71.04 including the 4-pin pigtail. Why should I need to pay Toyota for the OEM version at a higher price if the TK99FR works. Or maybe the TK99FR doenst actually work with the Grand Highlander?? Something is amiss here.

Jameson C.

1/26/2026

@Cough it is a little wonky with the Grand Highlander but the Tekonsha part # TK99FR is a kit that doesn't require the intermediate harness so for a 4-way it's the way to go.

Cough

1/27/2026

@JamesonC What exactly do you mean by the "intermediate harness" What I would call the four wire pigtail under the rear bumper? This is needed with every module?? AFAIK there is no siutation that needs another intermediate harness??

Steve C.

1/27/2026

@Cough You need 2 items. The module from either Toyota, Tekonsha or Curt, and the "dumb" 4-pin connector under the bumper. The Tekonsha TK99FR provides both. I can't tell you if it will work. I do know that the Curt module does not work on my Grand Highlander and the Toyota module does. Both Tekonsha and Curt claim to manufacture their own modules. What is unknown is if the internal electronics are the same. If they are, I would bet that the Tekonsha will not work either. Only way to know is to purchase it and find out for yourself. Or, just get the Toyota module, eliminate the hassle, and know it will work. If you go with the Toyota module, then you will still need the "dumb" 4-pin connector that connects under the bumper. You can purchase the 4-pin connector from Toyota as well but I thought it was overpriced.