Can I Replace My Trailer’s 4-Flat Plug With a 7-Way Plug for My 2022 Toyota Highlander?  

Question:

Expert Reply:

Hello Eric,

Thanks for writing in, I'm glad you found us.

Yes, you absolutely can replace the trailer’s 4-flat connector with a 7-way plug and only wire up the 4 existing functions if you want to stop using an adapter on your 2022 Toyota Highlander. The 4 wires would still handle your basic trailer lighting functions like running lights, brake lights, and turn signals, and the unused terminals on the 7-way plug would simply remain inactive until needed later.

For that setup, I’d recommend the Curt Trailer Connector Adapter # C57672. This gives you both a 7-way RV connector and a 4-flat connector at the back of the vehicle, so it’s a really clean solution if your trailer only currently uses a 4-flat but you may want the flexibility for other trailers down the road. It plugs into the existing 4-flat wiring on the vehicle and provides the additional 7-way functions if you decide to add them later.

If you think you may eventually tow a trailer with electric brakes, charge a trailer battery, or use other 7-way functions, then the better long-term option would be the Universal Installation Kit for Trailer Brake Controller # ETBC7. That kit includes the wiring needed to fully activate the 7-way connector, including the brake output wire and 12V power circuit. Even if your current trailer only uses 4 wires, this setup saves you from having to redo everything later if you upgrade trailers.

If you do swap the trailer plug itself to a 7-way, just make sure the 4 lighting wires are connected to the correct terminals inside the new connector. Most 7-way plugs are labeled, and matching the functions correctly will keep everything working properly without needing the adapter anymore.

What kind of trailer are you getting ready to tow with your Highlander, and are you planning mostly local trips or longer adventures this season?

expert reply by: Kate F

0

Louis G.

5/23/2026

I had trouble wiring it properly - do some research. I went through 3 of the flat four plugs and got disgusted with the cheap contacts breaking off (I almost had an accident because I didn't realize that the lights were off ) so i installed this one. Its a little stiff to seat into the male connector on the truck but a little dielectric grease or silicone spray works wonders. I think its been a couple of years now.