Charging wire - Event Date: 27 Nov 2016 - 10 Dec 2016

Originally posted by furpod OK, so far, near as I can tell, you don't actually KNOW what is back there. Correct? Before we go hacking up the wiring harness etc on a brand new computer controlled modern vehicle, lets make sure we NEED to. If Toyota did this, I PROMISE they didn't cut into your wiring harness anywhere. If the Highlander actually came with a factory tow package it WILL have a plug in pigtail for the trailer wiring harness. It probably has one in the driver's area for the brake controller too.. Just so you know, with modern cars and trucks, if you go hacking in extra wiring, lights etc, they often will give an error code, possibly even shut down, when they "see" the drop or increase in voltage on that circuit. Really. Your Toyota has more processing power then the Lunar Landing missions had access to. Just a quick look under the rear, at the back of the Bargman connector and you should be able to follow the wire bundle to see if it goes randomly, or to the factory harness.

Unfortunately, not all cars with factory tow packages come with a dedicated pigtail. My Escape (2016 SE with factory tow package) did ot have a dedicated connector for a brake controller. It came with a 4-pin connector. I needed to use the ETBC7 Universal wiring package from eTrailer. That is why I suggested that the OP refer to eTrailer in order to connect the brake controller. They were a great resource, not just for the equipment, but the expertise. They have videos that are helpful also.

I just checked on eTrailer. The Highlander will require the ETBC7 Universal Installation Kit or the equivalent homemade kit to connect it. Since the Bargman connector was already installed, the wire and breaker with appropriate connections may be the main thing needed. There will be two wires to run from front to back. The one is for charging. The second is connected to the brake connection to power the brakes. I'm not home, so I don't have the instructions available to look at, so I can't be more specific at this point.

OK, so far, near as I can tell, you don't actually KNOW what is back there. Correct? Before we go hacking up the wiring harness etc on a brand new computer controlled modern vehicle, lets make sure we NEED to.

If Toyota did this, I PROMISE they didn't cut into your wiring harness anywhere. If the Highlander actually came with a factory tow package it WILL have a plug in pigtail for the trailer wiring harness. It probably has one in the driver's area for the brake controller too..

Just so you know, with modern cars and trucks, if you go hacking in extra wiring, lights etc, they often will give an error code, possibly even shut down, when they "see" the drop or increase in voltage on that circuit. Really. Your Toyota has more processing power then the Lunar Landing missions had access to.

Just a quick look under the rear, at the back of the Bargman connector and you should be able to follow the wire bundle to see if it goes randomly, or to the factory harness.

Thanks. That's pretty straight forward. I just don't look forward to crawling around under the car...lol

Check out eTrailer.com since you will need to get an electric brake controller. You should get the information on wiring there. I don't know if the Highlander will have a specific harness or if you will have to get the generic harness like I did for our Escape. I chose the Hopkins InSIGHT Flex-Mount controller which has worked very well for us. Others choose the Prodigy P3 controller. In any case, you will need a controller for the brakes. Make sure it is a proportional controller.

If it has a tow package and a 7 pin, are you sure it's not sending a charge? If you are sure, then the answer is 10 gauge wire, fused with a 30A. The most basic, and with best possibility for it to cause issues in the future, is a wire right from the alternator or battery positive on your truck. The better way is a relay in line so the charge wire is only hot when the truck is running.

To check that it is or is not charging, start the truck, then use a multimeter to probe the two connections at 1 and 7 o'clock, with the alignment tab as "12 o'clock" you should see voltage. (I just can't imagine a dealer not using the factory harness, which should include a charge wire)