Trailer wiring for Tundra without tow package. Complete job.

Truck did not come with tow package so I'm doing everything myself and it's a piece of cake. Skip to post 16 to jump right to the install, click this https://www.tundras.com/threads/tra...tow-package-complete-job.128150/#post-3276326


Instructions for trailer wiring kit say to plug into the grey connector next to battery.
(picture A on page 2 found here: https://assets.curtmfg.com/masterlibrary/55378/installsheet/55378_INS.pdf)
The instructions make it seem as though the connector is open and waiting to be plugged into, but my connector is already connected to something. I'm curious what it's connected to and would like to understand what this component does. What is that I'm disconnecting when I go to plug the wiring kit into it?

Thanks.

It's too bad the truck is not a later model where they offer a single kit to provide the 7 pin connection. I'm stuck doing this 4 pin and then adding the 4 to 7 adapter and then running the wiring for brake controller, too.

 

etrailer | Trailer Wiring Harness Installation - 2001 Toyota Tundra - YouTube

 

There is indeed a grey one pin connector next to battery, O 3 Option Connector and it goes to the T 9 Trailer Converter located driver side rear.

 

This is a bit of dupe thread with my other one. Sorry about that, I tried to delete one but didn't see the option.
What's funny is that if O3 goes to T9 but it's currently hooked up to daytime running lights? The other thread it was mentioned that O3 is currently plugged into DRL.

Thank you for the response and attached info. I should be all set to get this thing wired up easily.

 

I want to say this is something @daveeasa was interested in managing, if you end up outlining a process and part numbers to use to make it a plug-and-play thing, that would be a hugely helpful contribution to the forum.

 

Sure. Unfortunately I've already ran the 2 wires back for power and brake control to the future connector at the rear. Also grounded the brake controller and tapped into the taillight. So the pics will start at this stage and I'll document the steps going forward. It's a little out of order because I'm waiting on the hitch itself, weight distribution hitch swap from other truck, the 4 pin wiring, and the 4-to-7 pin connector. But I already have brake controller so figured I'd get that set up and ready to receive everything else so that's why it's done early.

I can do the write up right now for the brake controller but it might be best to do it all in order. Hitch should arrive tomorrow or next day, and 4 pin just showed up. 7pin connector should also arrive tomorrow or next day.

1- install hitch
2- install 4 pin
3- install 7 pin
4- install brake controller
5- install weight distribution hitch

 

My truck has two grey 2 pos connectors between battery and fender. One for DRL and one foe power to the tow controller.

I have two Oem tow controllers and a modified Curt as well. All connect to the 11 pos connector (9 used) under the driver taillight.

output from the controller module feeds the hitch location 6 pos connector w 5 used supplying 4 pin plus reverse.

brake controller output and power for trailer battery are the two missing wires needed to complete a 7 pin.

as op mentions, no clean Oem 7 pin part available, must hack in from an alternate vehicle or year. I have a few of those too along with the Oem 4 pin output which is very much not special.

 

Anyway, the long and short of it is, should be possible to get power for the brake controller injected up front in the engine bay. Since the controller doesn't need tons of juice, nice to re-use OEM wire there if it's intact. Test the center pin of the 11 connector, should be fused power, ignition or battery is fine, the one I have is direct to the battery post in the fuse box and looks like an aftermarket piece there, yellow wire and had a tag on it, very non-Toyota, feeds the grey connector between battery and fender then OEM from there to controller.

that plus the OEM controller gets you 4 pin output + reverse at that 6 pos connector. Then you're just f'd b/c you'd run brake controller output and if doing that, may as well run power as well for trailer battery (if it has one but either way, 2 conductors isn't materially more than 1 conductor when running 12 or 14 gauge.

Then you also need power input and brake controller output into the cab through the firewall. So, fused power again, feeds brake controller which then feeds output to 7 pin along with a straight fused power.

For my own setup I think I'm going to run all this off the 2nd battery so that's a pre-req to get going. In the meantime, I have a 4 pin setup if I need to tow anything dumb. Someday I'll make progress.

So, yeah, don't think there is adequate volume for me to do a kit for this but happy to chime in / help like BubbaW only without his awesome diagrams and extensive background.

One thing I definitely could do is a feed from the 5 wires at the hitch spot into one of the 7 pin connectors, I have most of that stuff. But it'd still need the brake controller and trailer power so if hacking those, may as well just hack the whole shebang?

 

Couple of notes here.

14 gauge is fine for 1 or 2 axles. Anything bigger would need the 12 gauge.
14 gauge is sold in perfect length of 20' most commonly so going with that.
The extra power wire is certainly optional for anyone that does not care to charge their trailer battery while driving, or to run trailer off truck battery while parked and connected.
For those that do run this wire it's been said that prolonged connection between truck and camper could drain your truck battery so remember to unplug if concerned about that.
I like things clean so I always have colors consistent. But for someone that has a different color wire laying around and if they want to use that, I encourage to at least add colored electrical tape at both ends, as well as all penetrations, to show the true intended color of wire.

The power input for the brake controller is actually not a fused connection but rather from an auto-reset circuit breaker rated at 20 amps.
The auto-reset breaker for the trailer power wire is 30 or 40 amps. Both breakers can share a hot line from the battery or fuse box.

I'll take pics as I go along and write it all up as it happens.

 

I put on the first half of the 4 pin setup. It uses the T9 as noted above.
However, after the project will be completed the T6 will never be used.
What is the purpose of that T6 connector? Only thing I can guess at is yet another harness that provides backup lights to a 7 pin install. I'm born stupid and never owned a Tundra so I expect to be wrong. Tell me I'm wrong.

 

Takes the brake controller output wires, adds ground and reverse, exposes at the hitch. Makes plenty of sense to me, what’s not to like? The Curt module I have doesn’t bother using it but the OEM setup does.

 

I haven't read this thoroughly. Just throwing my info in the wind if not already spoken for, but I had a curt 4 pin harness that used that little grey connector on the silver truck.

It "powered" a plug that had a dummy in it on the back of the truck. I removed the dummy and plugged in the curt wiring harness for 4 pin flat.

Easy peasy. Save the dummy plug though because you might need it one day like I did

My 2002 V6 Tundra did not have DRLs and there was a dummy plug in the little grey connector in engine bay

 

I spent a lot of time looking into harnesses before buying the ones I did. Never saw one offered that delivered a ground and reverse to a 7 pin install using that connector. Kind of a shame that Toyota went through the trouble to add it and the aftermarket world didn't capitalize on it.

I plan on grabbing my ground from a bolt inside the bumper and have no use for reverse lights, but I'm sure others out there would buy it.

 

Some Oem part photos. I think one of the 7 pins is a 4 runner part. Not sure about the other one. Definitely no easy way. The trailer controller is a nice piece though. The rest may as well just DIY / hack and get it done.


^^ stock T6 to 4 flat


^^ T11 control module


^^ 7 pin option 1



^^ 7 pin option 2

 

Cracked one of my ribs yesterday so a bit of delay and slower progress than expected.
But progress was made anyway. The hitch receiver showed up today so it was time to work.
Gonna start the write up process now. It ended up being an easy day.

 

Step 1 - Hitch receiver.
I ordered the Curt 13184 Class 3, 2 inch rated for 5,000/500 or 7,500/750 with weight distribution hitch.
Link:

$187 CURT 13184 Class 3 Trailer Hitch, 2" Receiver, Fits Select Toyota Tundra, GLOSS BLACK POWDER COAT

https://www.amazon.com/dp/B002ELJZZE?ref=ppx_yo2ov_dt_b_product_details
Here's what I pulled out for this job:

Hi-lift jack, torque wrenches, step drill bits, sockets, drill.

First thing I did was measure the distance between the existing threaded weld bolts on the frame.
There are 3 bolts required on each side for this hitch. Starting with most rear looking forward, bolt 1 is an existing pass through hole in the frame. Bolt 2 is an existing threaded hole. Bolt 3 will require drilling. I measured the distance between both bolt 2s and it came out to be 39 inches for my truck.
I measured the distance for the corresponding holts in the receiver and it measured out to be 38 inches. So time to put muscle on it and open it up an extra inch.
Using my hi-lift and positioning the receiver carefully, it was easy to push out each side a little bit and get the desired distance needed for a perfect fit.

Getting under it(spare out of the way), I used my knee to assist holding the receiver up while I threaded bolt 2 into the existing threaded hole in the frame on both sides.
Once those were in, I put in bolt 1 on both sides. I tightened everything hand tight with ratchet but not overkill and no torque. This is all just to get it set up for drilling the holes for bolt 3. I used a tiny drill bit to get a little hole into the frame perfectly in the middle of hole of the receiver. I can't use the step bit to do the hole completely because it would eat into the receiver so with the center holes drilled I removed the receiver. Receiver off, I drilled out both sides to the required just over half inch. Now it was ready to be put back on again and torqued per manufacturer spec in the installation instructions(84 and 110).

All in all, not bad. Would have been much easier without a broken rib but what can you do. The final product looks clean and does the job. I'm happy with it.

 

Step 2 - 4 pin.
I ordered a 4 pin harness designed to work with 1st gen Tundra existing connectors.

$51 Curt Manufacturing CURT 55378 Vehicle-Side Custom 4-Pin Trailer Wiring Harness, Fits Select Toyota Tundra , Black

https://www.amazon.com/dp/B0009I4TUA?ref=ppx_yo2ov_dt_b_product_details

The first one is up front. Mine was under the battery tray. Only visible connector was the DRL. But every connector used here should be capped and not used, unless prior owner did something. Here is how dirty and hidden the connector(on the left) might be. It uses a fused connection yet they didn't include a fuse so I had to rob a 10 amp old school blade from my '85 truck.


I go to the back and pick it up at the other end. First mounted the converter behind the tail light.

Then tied into the harness under the rear driver tail light.

The 4 pin connector is done and ready.

 

Step 3 - 7 pin.
I ordered a 4 pin to 7 pin adaptor that came with a bracket mount.

Kohree 4 Pin to 7 Pin Trailer Adapter Kit, 4-Way Flat to 7-Way RV Electrical Round Blade, Trailer 4 Pin to 7 Pin Adapter Plug Connector Wiring Harness with Mounting Bracket for RV, Truck, Car

https://www.amazon.com/dp/B07V667F84?ref=ppx_yo2ov_dt_b_product_details
This adapter connects to the previous 4 pin connector and grabs a ground at the nearest bolt in the bumper.


Hot lead from battery started at a 40 circuit breaker fed by hot wire I shared with future brake controller 20 amp breaker.


From the cab to the frame behind the driver seat.


Pulled the grommet there and added a hole and fed it through.


Ran it all the way back. I use sheathing when it touches metal and might move around.


Black wire splices into 7 pin at the rear and power is done.

 

Step 4 - brake controller.
I ordered the Tekonsha P3 controller.
https://www.amazon.com/gp/product/B000P17NXQ?ie=UTF8

First step was to mount controller so I see how far the wires stretch under the dash before running wires. Want it close to inside with ability to tilt if needed.



Brake controller has 4 wires that need 4 things.
1 power = black
2 ground = white
3 brake input = red
4 brake output = blue

Black wire starts at battery positive and goes to 20 amp auto reset breaker, next to the 40 amp that feeds the black wire for the 7 pin.


Fed into the cab along with the black for the trailer into the cab.
There's the blue and black both coming in. Snap ring pliers help a lot to keep that hole open as you pass wires through there.


White ground wire connected to this bolt.


Red wire taps into green/white wire seen tapped here.
Found this by probing wires to see which lights up the tester when brake is pushed.


Blue wire goes all the way back with black wire from 40 amp breaker.


They end up back here with everything else.

 

Step 5 - weight distribution hitch.
I ordered the Draw-tite 49911 WDH with torsion bars(rather than chains) rated for 6,000.

$334 REESE Weight Distribution Hitch, 6000 lbs Multi

https://www.amazon.com/gp/product/B07YLCKJLJ?ie=UTF8

On second thought I feel a write up is not warranted due to nothing specific to Tundra and no tricks for this. It's a simple install following instructions from manufacturer. I did have to redo the top bolt on the hitch to add washers and get the proper load on the torsion bars, but other than it went off without a hitch, pardon the pun.

 

I just put a brake controller in my truck recently, it was not hard. I just ran some 10 gauge from the battery terminal, through a fuse, to the controller, and tapped the brake light directly off the brake pedal switch. After that it was just a matter of running a wire back to my 4 to 7 pin trailer adapter.

 

I do a lot of my house work and car work at night. As such, I need good light in the engine bay. I had some extra free time after getting the Tundra all ready for pulling the travel trailer so decided to step ahead and wire up some LEDs under the hood for night work. This will come in handy when I swap the timing belt soon.
The lights were a certain length that provided for an extra leg after making the loop. Since the driver side of the vehicle has more stuff + battery, I went ahead and ran the last of it on that side. I don't have OCD so no need for extra light on other side. Good enough.

 

Looks familiar. I thought this was my truck. Great minds think alike

This is how I did mine. Completely water proof.
https://www.tundras.com/posts/1851725/

 

Hi everyone. Have just joined the Tundra group.
Great info from everyone. Member RustyBirf
has solved my current question, connecting to brake light
for upgrade to 7 wire trailer hitch.
This is a copy of the post,
I would like to look at these photos, and am not able to open them.
Could some please help me with how this can be done?




Aug 3, 2023 at 1:12 AM
#19

RustyBirf [OP]New Member
Start a Conversation
Joined:
Jul 28, 2023
Member:
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Messages:
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2001 AC 4.7 2WD
Step 4 - brake controller.
I ordered the Tekonsha P3 controller.
https://www.amazon.com/gp/product/B000P17NXQ?ie=UTF8

First step was to mount controller so I see how far the wires stretch under the dash before running wires. Want it close to inside with ability to tilt if needed.



Brake controller has 4 wires that need 4 things.
1 power = black
2 ground = white
3 brake input = red
4 brake output = blue

Black wire starts at battery positive and goes to 20 amp auto reset breaker, next to the 40 amp that feeds the black wire for the 7 pin.


Fed into the cab along with the black for the trailer into the cab.
There's the blue and black both coming in. Snap ring pliers help a lot to keep that hole open as you pass wires through there.


White ground wire connected to this bolt.


Red wire taps into green/white wire seen tapped here.
Found this by probing wires to see which lights up the tester when brake is pushed.


Blue wire goes all the way back with black wire from 40 amp breaker.


They end up back here with everything else.

 

From this thread: https://www.tundras.com/threads/trailer-wiring-for-tundra-without-tow-package-complete-job.128150/

Unfortunately, it looks like @RustyBirf was hosting the photos in Discord, as a few other members do. Unfortunately, for images hosted off-site, Tundras.com has no control over their existence. Rusty would need to check his Discord to confirm the images are there, and shared to the world.

But he hasn't signed on since this time last year (Sept 2023), so I don't know how reasonable that is. You may be able to use Wayback or similar tools to see if there's a cached copy on the internet, but I'm doubting it.

 

Hi shifty,

Thanks for fast reply. I think I'll go by Toyota to see if there is an easier place to tap into the brake light switch.
Want to connect the Blue wire on the Tekonska Brake Controller, going from 4 pin to 7 pin.
Thanks again, happy motoring to you.
J

 

I T’d the third brake light when I replaced it. That nets cargo for bed lights which is a nice bonus. But probing for brake switch + is straightforward to me, just trace the wire to an accessible junction.

 

That is an excellent solution.
Thanks