"Factory" 7pin Trailer Harness Installation

To fully answer this, My truck has the 5 pin (T 7) connector for the brake controller but does not have the Towing Brake fuse. I just checked the battery lead (Black wire, pin2) and it does not have power, obviously. I haven't gotten around to putting in my brake controller or I would have realized that sooner. Now to track down where that wire stops at, maybe at connector IA4.

 

I will check this when it's not soo hot out..
IA4 pin1

 

Alright there's the culprit, the fuse side of IA4 Connector pin1 does not have a pin.

 

Have you check the fuse slot in the engine fuse & relay tray for the missing pin to hold the fuse?

 

Man, I'm slacking.. I don't have the fuse/pin in the fuse box. I even took pictures and forgot to post them. I'll probably put a pin in IA4 pin1, and then run a wire out to my Bussmann fuse box.

 

You got the part number for the brake controller pigtail? It's suppose to come with vehicle...but

 

I got the pigtail with the controller I bought.

 

In regards to the missing relay and etc, have you guys seen the following thread? It might give you some ideas?

https://www.tacomaworld.com/threads...er-wiring-without-factory-tow-package.412366/

 

I pretty much followed this write up in adding a 7 pin to my truck, but wanted to add a couple of pictures and some insight I gained from doing it.

First of all, I bypassed putting the wire in the factory location to power the brake controller. One could probably get the correct fuse box connector at the junk yard and keep it totally factory, but I wanted to up-size the wire anyway, because I think Toyota's wire size for the 30a fuse is on the small side. To power it, I just spliced into the wire harness adapter for my brake controller; just before it plugs into the factory harness. Nice, clean, strong, soldered joint covered in adhesive lined heat shrink. I used 10AWG. I ran this along the main harness into the engine bay and connected it to the battery through a 30amp breaker.

I also felt that I wanted to up-size the wire running to the trailer brakes from what the OP mentioned, so I unwrapped the factory 4 flat harness and ran 2-10AWG wires with it. One for the trailer brakes, one for +12v at the trailer (it went along the main harness through the firewall as well, and got tied to the battery via a 30a breaker. I didn't want my +12v switched, but you could- just a relay and switched source.). I had to use the next size larger loom to wrap the harness back up, but it looks totally factory.

I liked the OP's method of tapping the reverse light using an old trailer wiring harness- just took me a bit to figure out how to do it. I finally figured there are keepers you have to pull out in the 6-way connectors, then you can pop the terminals out by lifting the little latches that keep them in. Then just take the extra wire from the old passenger-side 4 pin harness to get the wires needed to complete your reverse light tap.

I'll get more pictures later!

 

Good job! I certainly appreciate the critique and additional input! I think your upsizing of wiring is a bit overkill, here is a couple diagrams that I reference for length/gauge/capacity of the wire. Of course overkill isn't a bad thing in this case. It's just kind of puzzling that Toyota (and probably other manufacturers) use smaller gauge wiring than what I would be comfortable with for certain circuits.

Offroader chart (source/accuracy unknown)


US Coast Guard chart (probably overkill, but for good reason)

 

Okay bump for a question regarding this install.

I have a '13 Regular Cab (base model 2wd), and I have routed the 4-pin harness all the way through the truck. Before I get any further, I wanted to see if the pigtail for the Tekonsha P3 I bought would plug in, however I'm having difficulty finding it (connector T7). Half the dash is apart already for the 4-pin harness install, so visibility is pretty good, I just cant seem to find the connector for the P3. Does anyone know if base models do indeed have that connector?

Okay, after some research it seems that no 2TR-FE equipped models came with the T7 connector in the kick panel area of the cabin (dammit). What are my options now? The factory Tekonsha pigtail has ground, power, brake control and
stop lamp. If I simply tap into the existing yellow wire running to the tailgate, that should fulfill the brake control portion of things. I'll have to figure out where the 30A fuse runs to, since like Sandman said, it doesnt seem to make it to the IA4 connector. If that goes well, and since ground is easy enough to secure, all that's left is the stop lamp. Where can I tap into for that?

 

Same wires and colors from '05 ~'13.

 

Thank you. Ended up routing power directly to the battery, but those pins were helpful in getting the signal wire to the controller. All good after the maiden tow with everything working great.

 

What is a "BRAKE LIGHT/CONV MODULE 08921-04820" that sits in a compartment right behind the driver seat on my 2001 Tacoma Pre runner extended cab ? What does it do ? My mechanic doesn't know. Anyone ?

 

It takes the signal input from the vehicle harness (Stop, Left Turn, Right Turn, Hazards) and provides appropriate selection to towing harness.

 

Thank you for making this thread. Very helpful. I've come to realize how much value the $500 optional factory tow package really is (remember the transmission and oil coolers as well)

I also have the T7 connector buried in kick panel and I'm in the middle of attempting this stuff - trying to copy factory as much as possible, I'm not worried about the 16awg wires - and have some questions:

Your step 6: where does the true factory 7pin towing harness pull the reverse light signal from? Does it come from the tail light via BE1 connector? I'm worried about overloading that circuit because I already spliced aux backup LEDs into that. Also test pulled the 30amp towing tail fuse seen in the right of your pic here and all my tail/reverse lights still work... so that's another circuit then but the trailer reverse lights are not??

Btw, what is the 30amp towing fuse for that's hidden under your fog relay in that picture? I have that too but not sure what it does...

I went to a junkyard this week and snagged the oil and transmission coolers. Since I was already there I also scored the back/engine side of the IA4 connector with about a foot of wire lead. Harness was already chopped and fuse/relay box sold or I would have bought that too. I'm installing a bussman aux fuse box so I'll probably run the trailer brake power wire there. Unless I can find the right terminal for the stock fuse box and then just pop in a 30amp fuse in the slot.

Now where does the stock 12V+ wire run? I could probably go back to the yard and pull it but first need to know where it hides. I also have the entire ID2 plug (with the yellow wire you stuck in it) and that whole part of the harness that goes outside under th driver seat and to the back of the truck ending in a connector (the bigger one from the first picture of this thread). I'm wondering if the 12V+ is already in there...

 

I think I made some progress last night. Here are some pics of the harness I got from the wrecker. This one will replace my entire left side body/frame harness from the kick panel down to behind spare tire




Note how this connector Which I think is called IB1 (plugs in on the right side next to the IA4 plug) has 4 extra wires (green/black, greyish and 2 red/blue ones) that my truck didn't have.
I traced them to the BE1 connector in my upper pic. I suspect that those are for 12v+ , trailer reverse lights and other stuff I'm not yet sure of...
Not sure yet what's on the fuse side of those extra wires either

 

Noticed my alternator fuse is 120amp.

I already upgraded my stock alternator to the 130amp which comes standard on the tow package equipped trucks.
Does anyone know what size fuse those use? I'm thinking should be at least 130, no?

 

I believe it's 140amp

* 18:w/ Trailer Towing
* 19:w/o Trailer Towing
* 20:w/ Power Outlet (115V)