12V Aux line to trailer for base model no factory tow package

I'm running a 12V line back to my trailer connection for a base model 2017 Taco with no factory tow package. When I did this on my old F150, there was a slot for a relay that turns on this 12V aux line, and all I had to do was plug a relay int here and I was good to go. On another vehicle I had to install an aftermarket 30 amp 12V relay, and find some 12V actuated by the ignition to run it.

Of course one could run this 12V line directly off the battery through a fuse, and then park their trailer out in the boondocks, and have a dead starter battery in the morning. I'm not going there!

I've been searching around for a wiring diagram for the 2017, Mitchell's has one for $45 for a five year subscription or $18 for a month, so far I haven't found one floating around these forums yet.

Also looking for the relay diagram, to find out if there's a factory 12V Aux line relay I can put in.

[EDIT] Well it looks like there is a 12V trailer relay installed, and a 30 amp fuse for it. There is an empty plug back near where the trailer connection is supposed to be. Apparently that's nothing to do with trailers though. I can't find any handy terminals or big wires near the under-hood relay box that seem to be switched with the ignition. If I hang an extra relay here, coil to the ignition, and put in a 30A fuse then I have a safe hookup for 12V Aux powere to the trailer, but it looks like I'll be installing this the hard way, whatever that is.

[EDIT] Ok, OK, I get it, I have to bring my own towel and soap and take a bath before I come back here if I ever had an F150. Hey, people make mistakes but it doesn't have to mean I am scarred for life!

 

No man, you are good -- hell, we even welcome the -- (cough) -- Dodge guys here...

Welcome to Tacoma World

 

Hi, could you share the location of fuse, relay and wire near hitch please?

I also need to do this for a 4wire trailer install. Thanks in advance

 

If the bumper does not have the towing outlet, then there's no incomplete tow harness. The connector you see is most likely the missing bumper parking sensors.
For the 4 banger missing the tow harness outlet, you'll need to install an aftermarket towing combiner which will need a fused line to the battery, unfortunately.

 

Assuming you have an actual complete wiring harness kit like a Curt or Hopkins, the fused line to battery is the + supply of what is essentially a potted relay that supplies power to the trailer wiring brake lights and turn signals on demand. There's no risk of dead battery.

 

Well, for the 4-wire trailer hitch, you can get a Curt or a Hopkins adapter kit that plugs into the tail-lights. That's what I'm starting with. But to install a 7-blade connector with Aux 12V, there needs to be a separate, heavy 10 gauge 12V line back to the battery or fuse box. I'm trying to figure out if Toyota already ran that for me or if I have to install it myself.

 

Agreed. I have a Hopkins wireing harness kit coming that just plugs into the lights. It's a 4-wire kit, but as soon as I am done with my soldering iron it willb e a 7-blade kit too. It's that 12VAux line I'm trying to put in, and want it on a 30A fuse. This is additional to the small 12V line that runs that isolating relay in the Hopkins wire harness. I'm hop[ing someone solved this problem before and can tyell me the easiest way to do it.

 

I investigated this extra plug, and it's dead 0V with the ignition on, ignition off, lights on etc. So it's something else like the parking bumper sensors you mention.

 

I knew a guy that said if you owned a Datsun pickup (Remember Datsun - the company so ashamed of their reputation that they changed their name to Nissan?) you needed to bring your own towel and soap, and take a bath outside before you come inside his house. This has now become an inside joke among my buddies - all they have to say is "Bring your own towel and soap" and we bust out laughing. "I have a Ford Pinto!" "Bring your own towel and soap then." "I use Chinese locking pliars instead of Vise Grips." "Bring your own towel and soap then." "I like Anchovies and pineapple on pizza!" "Bring your own towel and soap then."

 

I found a set of wiring diagrams on here finally. So far I haven't found an easily accessible 12V wire that is switched on with the ignition. Done a lot of poking around in the relay box in the engine compartment, mostly. The best I can come up with, without cutting open a wiring harness, is to hang a 30A fuse off the battery, heavy 10 gauge line to an aftermarket relay, and then to the trailer Aux line. If I run the coil of the aftermarket relay from the marker lights, and remember to run my lights whenever I'm pulling the trailer then my trailer has 12V aux power to run stuff when the truck is on, no power draining the truck starter battery when the truck is off.

I'll see if I can scan a diagram of this. Also try to figure out if I can link to the whole wiring diagram PDF. Wish the damned thing had an index.

 

OMG I didn't know this was a thing: Fuse taps!

$8 Auto Car Add a Circuit/Add a Fuse Mini Low Profile ATM TAP Fuse Holder Automotive

https://www.amazon.com/dp/B00EO571Z4?ie=UTF8

Find a fuse that's switched with the ignition and just tap it! I wonder if my local auto parts store will carry these.

 

And apparently some people are hacking one of these aftermarket fuse panels (meant for marine use it looks like?) into their tacomas - not sure how it all works yet but work looking into if I need to add more that one or two circuits:

$50 FUSE BLOCK STB 12SPLIT W/GND/CVR

https://www.amazon.com/dp/B00WM2MWQ4