A CURT custom wiring harness (also called a T-connector) is a simple, plug-and-play electrical device that eliminates the need for cutting, splicing and soldering when installing vehicle-to-trailer wiring.
Most vehicles do not come ready to tow. Unless your vehicle has a towing package, it is probably not equipped with a trailer wiring connector. This is where CURT''s custom wiring harnesses come into play. Custom wiring harnesses plug into your vehicle''s electrical system using original equipment (OEM) connectors. Our custom wiring harnesses use two or more OEM connectors to plug in at the taillight assembly and provide a standard trailer socket to allow a trailer to be plugged into your vehicle''s power system.
This harness provides a 4-way flat connector socket and comes with a circuit-protected converter. It is designed to be a custom wiring harness for certain years of the Toyota Sienna van (to verify your vehicle compatibility, see the CURT application guide at curtmfg.com). CURT custom wiring harnesses are long-lasting and quick to install. They come with dust covers to keep your connector clean when not in use and feature a one-year limited warranty to give you peace of mind.
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To go from the drivers door into the engine compartment - follow the large bundle up under the dash. It will go behind the gas release and brake. Right above the gas peddle the bundle passes through the fire wall. Follow that same path and use a couple of tie-wraps to make sure it does not fall onto your feet while you are driving. There is a little hole in the grommet going through the fire wall that looks to be designed to have a wire pass through to the side. While I could get screw drivers to pass through - the wire would never go. On the other hand, you can push to wire through on the side of the grommet. I did that. I then continued to follow wire bundle to when it connects to engine compartment fusebox. Again - use tie-wraps. In the 2014 - which I have - this is right next to the battery... and you can attach the wire as shown in the various videos.
Agreed on the 12 V power routing - not ideal
I agree - the suggested 12 V power routing is not ideal - actually it is terrible. The 2014 Sienna has a place in the door jams for the wire - like Toyota thought someone might actually need it. I have a series of picture I would be willing to forward to Curt - for you to update your instructions. (I still have not found the route through the fire wall yet - but I will get that done soon.) Otherwise - this is an easy to put in system that seems to be very well designed. (You lost a star for the silly route for the 12 V line.)
Straightforward, but Toyota makes it hard to wire to 12V
The included instructions for this are good. Better yet are the videos on YouTube from the big online hitch distributor. Similar videos for prior Sienna years showed similar info with a little different angle, etc. So the instructions are excellent for installing the rear end converter box and adapter plugs. BUT...Wiring to 12V at the front of your van is not explained well on paper or in the video. Curt and the videos recommend routing the 12V under the car, along the brake line for example, which seems bad. You won't find any other wires under your car, so there must be a reason. Toyota apparently doesn't have a better trailer wiring solution so go ahead and buy this one. Routing 12V inside the van seems much better, and is what the "official" Toyota instructions suggest. Toyota DOES have better instructions that allow me to route the wire inside the van, under the door thresholds with other wires. I found a PDF of the Toyota instructions, with great color photos, in a separate Sienna forum. I wish Curt would adapt Toyota's instructions into their own. The need for 12V battery routing is not a Curt problem. Lots of models now need separate trailer light power, and this approach actually helps preserve function of your car lights, if your boat trailer lights get wet at the boat launch, for example. Be careful pulling off the Sienna light assemblies. The factory wires are short and not very thick, so they can't support the taillight bezels. Remove them slowly and support them so you don't yank those short wires.
Installation is a breeze
I installed this wiring on my 2011 Toyota Sienna and was extremely impressed with the quality of the wires and connectors. Connectors slipped onto the Toyota connectors with no problems. The only thing that was unexpected is that you need to run a wire up to the battery. The reason is that the vehicle has LED tail lights, so it is not designed to drive a big incandescent light like you would find on a trailer. (See Sienna owner's manual.) Therefore it needs the battery connection for it's active lamp drivers. I was impressed that the wire they give you to run up to the battery is rated at 125 degrees C. They really thought of everything to make this a reliable install. The instructions show routing this wire under the vehicle, but living in Minnesota, I don't like the idea of things dangling under my vehicle that could build up ice and slush, so I routed it through the vehicle interior with no problems. Removing the door sills is very easy. (There is an easy way to get through the firewall on the passenger side behind the glove compartment. However, going this route you will need to splice in a few more feet of wire than what is supplied.) This is a quality unit and I highly recommend it.