Adding 5-Way Harness to 2018 Toyota Highlander With 4-Flat

Published 10/01/2018

Question:

Yes, I have two boat trailers. One has a 4 pin flat (no brakes) while the other has a 5 pin flat (with brakes). The 5 pin flat includes 12V when in reverse to disengage the trailer brake when pressure is put to the hitch ball. Backing up is the same as stopping with regard to force, thus the 12V override. The Highlander comes factory with a 4 pin flat which is fine for the one trailer without brakes. Right now I tow with a Sequoia which has a 7 pin round and I use the adapters 7 to 4 pin flat and 7 to 5 pin flat. The 7 is pre-wired to provide the 12V when in reverse on the correct pin of the 5 pin flat. I am thinking that one solution would be to remove the Toyota wiring and install your 22119. Otherwise i would need to splice into the reverse light to get the 12V but that is less than ideal circuit wise. AS well as still needing a 4 pin flat for the other trailer.

asked by: Steve A

Expert Reply:

I'm a bit confused by your question; the Highlander you are getting has just a 4-pin flat, is that correct? And you are looking to tow a trailer with a 5-flat?

expert reply by: Kyle S

Steve A.

10/1/2018

Kyle S.

10/1/2018

Thanks for that info and I see what you are saying. You do not need a 7-way at all; the only thing you need to add to the 4-way on your Highlander is the 4 Pole to 5 Pole Trailer Wiring Adapter # 20036. This adapter simply splices into the reverse light wire on the Highlander which you can do with the quick splice that is included with the adapter. That will allow you to use one connector for both of your trailers. I have added a link to an install video of this part on a '15 Highlander as well as a link to a help article on trailer wiring that I highly recommend checking out.