7 Way Trailer Wiring Harness DIY (4 Viewers)

Joined
Jan 25, 2007
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545
Location
Winter Park, CO.
After looking around for a used 7 way trailer wiring harness(Toyota pn: 82177-60010, Wire Frame No. 4) and having no luck, I decided to build my own. The Toyota price of $210 + shipping was riddiculous to me for what that is. I wanted to stay as stock as possible in this and avoid cutting the wires at the connector. I used Toyota parts wired to a generic 7 way connector mounted to the Toyota bracket on the factory trailer hitch. The Toyota 7 way receiver that mounts to the bracket is NLA from Toyota. It was used across multiple vehicles around that time so they are out there in the used market. The couple that I found were in pretty bad shape from corrosion which is why I went with generic here. The install is as factory as it can be without using the actual Toyota wiring harness and 7 way. Without the Toyota harness I built this for about $60 in parts. Well worth my time, IMHO.

This is an easy half :banana: job.

The parts necessary to do this are(Toyota prices are from 4/4/18, YMMV):
  1. Female housing connector - Toyota pn: 90980-10895(1) - $7.50
  2. Repair wire(12ga) - Toyota pn: 82998-12480(1) - $5.25
  3. Repair wire(14ga) - Toyota pn: 82998-12440(6) - $5.25ea/$31.50 total
  4. Terminal plug - Toyota pn: 90980-09325(1) - $5.25
  5. 12ga wire, 14" length - white(1)
  6. 14ga wire, 14" length - 1 of each color: red, black, brown, green, yellow, blue
  7. 14/16ga ring terminal(6)
  8. 10/12ga ring terminal(1)
  9. 14/16ga heat shrink butt splice connector(6)
  10. 10/12ga heat shrink butt splice connector(1)
  11. 14/16ga heat shrink tubing
  12. 10/12ga heat shrink tubing
  13. 3/4" wire loom, 2' length
  14. Hopkins 7 way trailer wiring receiver with mounting bracket
  15. 7 way trailer wiring reciever(if you want to stay Toyota with the recessed mounting location) - Toyota pn: 82953-60020(1)
  16. Electrical tape
  17. Dielectric grease(there should be some in the receiver package)
  18. 4" zip ties(3)
Tools needed:
  1. Phillips head screwdriver
  2. Wire cutter
  3. Wire stripper
  4. Terminal crimper
  5. Lighter or heat source for heat shrink material
  6. Drill/bits to mount the Hopkins reciever to the factory bracket(if not using the Hopkins bracket)
I did this on my '06 LC. I believe the wiring to be the same back to '04, likely '03 as that's the first year of the revision from the '98-'02 models. This also applies to the LX as well. If you have not already, download the available 2004 wiring diagrams or use the wiring diagram for your year if you have access to it. The download is here: https://app.box.com/s/x5vfksi7bxz3tsr5r8n1. Plates 158/159(pages 259/260) have the actual trailer towing diagram. Use this to double check the wires on your truck to the connector(BX1 in the diagram) and from BX1 to the 7 way receiver.

I double checked the wiring in my truck vs. the wiring diagram and it was the same. I also made sure the contacts were clean in the male plug on the truck. They weren't in bad shape but were a bit tarnished from being exposed for an unknown period of time. I also checked for continuity at all the contacts.

The length of wire and loom should be just enough to give you the option of mounting either in the factory recessed location or in the location next to the hitch receiver. Feel free to cut to whatever length is right to you.

Read through the entire procedure before performing the work.

Assemble all your parts and tools and proceed.
  1. Strip the ends of all wires 1/4"
  2. Attach, using butt splice connectors the repair wires to the 14" wire sections. The single 12ga repair wire goes to the 12ga white wire. Heat shrink the connections.
  3. Pull the plastic insulators off of the ring terminals(if present).
  4. Slide a 1/2" piece of heat shrink tubing over each end of the colored wires and crimp the ring terminals to the ends. Slide the heat shrink over the connection to the ring terminals and shrink them. Steps 3 and 4 can be eliminated if you want to use ring terminals with heat shrink connections. I didn't have any so I did steps 3 and 4.
  5. Now you're ready to insert the repair wire terminals into the connector housing. Familiarize yourself with the connector and the numbers for the terminals on the backside of it. This is an 8 position connector but only 7 will be used. Positions number 3 and 6 are not labeled. Position number 6 is not used. The diagram below is for reference of terminal numbers. The perspective of the image is that of looking into the front side of the connector.
  6. First insert the plug(or packing as Mr. T calls it) into position 6. Push it in until flush.
  7. Next assemble each terminal into the connector, starting with postion 1 using the pinout below as a reference as to what wire goes into which position. The opening on the terminal faces downward in the connector. You should hear a light "click" when the connector snaps in place. Push in the packing around the wires as you go.
  8. Position 1 = red wire to left turn signal/stop lamp
  9. Position 2 = green wire to tail light
  10. Position 3 = white 12ga wire to ground
  11. Position 4 = brown wire to right turn signal/stop lamp
  12. Position 5 = blue wire to trailer brake
  13. Position 6 = unused
  14. Position 7 = yellow wire to reverse lamp
  15. Position 8 = +12v battery charge
  16. Once the packing is pressed in flush, make your connections to the 7 way receiver. Follow the pin out in the packaging for the 7 way. The connections are universal. Use dielectric grease on all the connections.
  17. Zip tie the wires together to keep things tidy.
  18. Wrap the loom around the wires. You will need to trim it down to the correct length. Use the electrical tape to hold the loom together and on the ends to hold it in place. I wrapped the entire loom with the tape to seal as much as possible as there is an opening at the point where the butt splice connectors are. You can stagger them for a more sleek build if you want.
  19. Install the 7 way to either the bracket that came with it or to the Toyota bracket. If using the Toyota bracket, you will need to drill some holes to which the bolts for the 7 way can mount.
  20. Mount the bracket and 7 way and plug in the connector. Double check the wiring at the 7 way and you're done! If you get some wires accidentally inserted in the wrong position, they can be removed by pushing in a pin from the front side of the connector on the underside of each pin and then pull the wire out.
Here are some pix for reference...

The parts I got from Toyota: Disregard the extra 12ga repair wire. It isn't necessary.
Hpn4PMA.jpg


The connector pin out: Note, the pin numbers are also on the back side of the connector.
iViPJiJ.jpg


Harness ready for 7 way:
8uga5Qi.jpg


7 way wiring:
VyK0iCT.jpg


7 way wired and attached to Toyota bracket:
83vihYT.jpg


Wires wrapped with loom and electrical tape:
VuVhelh.jpg


I will post up some pix of it mounted on the truck in the near future but I take it off when the weather gets nasty here in Colorado.

I hope this helps anyone looking for this kind of option.
 

reznunt

Massive Metal Shop
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For my 98, I only have four wires at my factory plug, correct?

*Nevermind, I can't do it your way. I will use a T-One harness with a hopkins 7-pin socket. Thanks for sharing!
 
Last edited:
Joined
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Messages
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Winter Park, CO.
That’s what I’ve read. I think the 98-02’s were only wired for the 4 way. Someone correct me if I’m wrong there. That’s how my 80 was. That one took a bit more work to install a 7 way with full functionality.
 

reznunt

Massive Metal Shop
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That’s what I’ve read. I think the 98-02’s were only wired for the 4 way. Someone correct me if I’m wrong there. That’s how my 80 was. That one took a bit more work to install a 7 way with full functionality.

Ya I wish it was plug and play for a 7 pin connector! In addition to plugging in the T-One harness, I have to pick up three connections from different locations on the truck to supply the 7-pin socket. Anyway, clean build! I'm sure this will help some people on here.
 
Joined
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Syracuse, NY
Thanks for the write up, it was helpful in quickly identifying the needed parts and pinout. Because the tow reciever blocked the factory 7 pin plug mounting bracket, I decided to design and custom fabricate my own. Fired up the CNC plasma table, cut it from 11ga steel, bent into shape, primed and painted. Grabbed some M8x1.25 10.9 bolts to attached it to the tow frame and stainless hardware to attached the plug to the bracket.

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Joined
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Syracuse, NY
From there I drilled and tapped the tow receiver frame, soldered up the harness, wrapped it and mounted. Works great, and complies within the linear departure angle.

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Joined
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Joined
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OOOOHHH! I like those! How hot do they have to get to work?
Not very hot. That's a small heat gun is used for remote control aircraft wing fabric. I bent up some metal to help wrap the hot air around and keep heat localized. I've used in very tight spaces on 100 series, works great.

Google it and you'll see they use very high end heat guns. My low tech gun works very well as you can see in video. Not sure if a good hair drier would work, but if high wattage I'll bet it would.

You can borrow my heat gun anytime or just use here.
 
Joined
Jan 25, 2007
Messages
545
Location
Winter Park, CO.
Not very hot. That's a small heat gun is used for remote control aircraft wing fabric. I bent up some metal to help wrap the hot air around and keep heat localized. I've used in very tight spaces on 100 series, works great.

Google it and you'll see they use very high end heat guns. My low tech gun works very well as you can see in video. Not sure if a good hair drier would work, but if high wattage I'll bet it would.

You can borrow my heat gun anytime or just use here.

I keep that in mind.

Thanks Paul!
 

Dparo

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Where that whip plugs into the female end is there another disconnect point or does it run from there into the dash?

My female end has a large chunk missing from it.
 
Joined
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Messages
545
Location
Winter Park, CO.
Where that whip plugs into the female end is there another disconnect point or does it run from there into the dash?

My female end has a large chunk missing from it.

In don't know but if there are any connections between there and the dash, it will show up in the wiring diagram.
 

gregnash

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Ok resurrecting this as I am going to need a 7-pin plug later this year and just called a local shop. With a brake controller and doing the install they wanted $700!!!!
Yeah I am planning on using one of the Curt Wireless Bluetooth brake controllers and was looking at wiring up one of these Hopkins 4+7-way adapters to the current system. Have a feeling that the wires on the 4-pin side may need to be moved around a bit depending on Toyota's wiring for the trailer.

The adapter that @uzj100 posted up is for a different year 100 than mine (98) so it won't fit.
 

PabloCruise

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Oh CRAP! VERY VERY glad I found this. Wife totaled the OEM 7 pin connection going through a water crossing a couple years ago and this year we bought a trailer. I made the thing work with zip ties but THIS is awesome!!!
 

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