What does "pre-wired" mean in reference to the Tow Prep Package?

aretesys · Jan 12, 2013

I just bought a 2013 Sienna L, and it has the Tow Prep Package for $220. I understand that the package includes mechanical components like a larger radiator, transmission cooler, etc, but I've also been told by my dealer that it is is "pre-wired". According to them, that means there is a wiring harness already installed in the rear underside, accessible by taking off the undercover, the large grey piece just in front of the rear bumper.
However, a local Trucking Thunder dealer says that "pre-wired" means nothing, and that they will probably thus have to run wires from the rear up the battery in the front, etc.
So my question is what does "pre-wired" really mean? Does it mean that there is an existing harness as described by the dealer that a separate towing harness can be plugged into? Or does the installer have to run wires up front, hook to the battery, etc.
I plan on hauling a Coleman pop-up camper with a 7 prong plug and electric brakes, as I did before with my Previa, but I'm not worried about the 7 plug. I just want to know if there really is something installed in the rear that will save the time and hassle of running new wires.
BTW, it appears that the tow prep package is the same for the 3rd generation Siennas, from 2011-2013.
Thanks much

erik m. · Mar 29, 2013

I just wired my 2012 today. It was not "pre-wired" in any sense.

brian_bp · Apr 2, 2013

The Toyota dealer's description of pre-wiring is reasonable. The other shop may be referring to the need to run wires for the brake controller and trailer battery charging, even in vehicles that are pre-wired for trailer lights.

Unfortunately, to my knowledge, the Sienna has never been available with pre-wiring, in any year or version, with or without the mechanical towing prep package. Other Toyota models are, particularly trucks.

Cmcfeters · Apr 5, 2013

erik m. said:
I just wired my 2012 today. It was not "pre-wired" in any sense.

Toyota's "Tow Package" is very deceiving as it doesn't involve a hitch or wiring. Just wired mine in under 2 hours, wire tapped into brakes/signals, installed brake controller & 7 wire plug.

janward12 · May 3, 2013

I got my 2011 Sienna with the "towing package". The previous owner had added the hitch itself, but had not wired the lights. On the right side where the jack is, I have two plugs ready to go, but the wires are very small leading me to believe they are designed to carry current for the LED tail, turn, and stop lights. I'm afraid if I splice into them to attach my trailer light wires, I will blow all the circuits because the trailer bulbs are incandescent. I really don't want to purchase the whole wiring package because I think I already have all the T-connectors installed. What more do I need to do to get my trailer lights working?

Riverdaze · Jul 6, 2013

Hey Janward12,
Did you get you wiring issue figured out? I am having the exact same concerns - small wires for LED tail lights may not support the incandescent trailer lights.

n8dogg · Jul 6, 2013

I can't speak for a 2013, but my '04 had a 4 pin connector hiding inside the rear bumper. I too wanted a 7 pin, so I had to install a couple of lines through the vehicle to run a 12v charge line and brake controller. In the event that you don't have the 4 pin connector, online sources (such as etrailer.com,) have a wiring harness kit that comes with a signal booster to provide power for the trailer lights. It still requires a 12v source to recieve that power, might as well install that while you're running your charge and brake lines.

brian_bp · Jul 7, 2013

n8dogg said:
I can't speak for a 2013, but my '04 had a 4 pin connector hiding inside the rear bumper.

That's good, but I don't think that was part of the 2004 towing preparation package; someone likely installed the trailer light wiring kit as well.

What does "pre-wired" mean in reference to the Tow Prep Package?

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