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DIY Trailer Harness for Model Y

NaperY

OD 1/8: MYLR5 - Changed 4/14: MYP
Mar 5, 2022
27
21
Naperville
I'm always a bit nervous about 3rd party supplied connectors, plus multiplying it over an extra 4 times. I'd much rather splice and solder the cables, then i know if i have light(s) out on the trailer that it 100% is the trailer lighting and not the car's.
 

NaperY

OD 1/8: MYLR5 - Changed 4/14: MYP
Mar 5, 2022
27
21
Naperville
Any information? Because, I am in the same situation.
I found an update in a service bulletin. I'm guessing because of the chip shortage, Tesla installed different body modules in 2021/22 MY with tow package than without. The service bulletin says that if folks opt for the post-delivery tow hitch installation that the LH Body Controller module would also need to be replaced.
just a hunch, but makes sense why the rear trailer light harness is dead.

Screen Shot 2022-08-29 at 11.44.32 PM.png
 

Attachments

  • Model Y Controller.pdf
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Last edited:
Trying to get this excellent thread revived - has anyone tried this on a 2022 MY? I'm about to give it a try and wondering if there's any experience/differences noted with the 2022 model, which seems to have changed a few things (I have the 15V Li-ion battery). Just installed the Draw-Tite 76430 hitch and the ZCI zero contact trailer wiring kit as a placeholder, but I eventually need trailer brake support.
 
Trying to get this excellent thread revived - has anyone tried this on a 2022 MY? I'm about to give it a try and wondering if there's any experience/differences noted with the 2022 model, which seems to have changed a few things (I have the 15V Li-ion battery). Just installed the Draw-Tite 76430 hitch and the ZCI zero contact trailer wiring kit as a placeholder, but I eventually need trailer brake support.
Whoops - "revive" probably wasn't the right term; the forum was hiding the most recent posts from me. Gonna try out
Trying to get this excellent thread revived - has anyone tried this on a 2022 MY? I'm about to give it a try and wondering if there's any experience/differences noted with the 2022 model, which seems to have changed a few things (I have the 15V Li-ion battery). Just installed the Draw-Tite 76430 hitch and the ZCI zero contact trailer wiring kit as a placeholder, but I eventually need trailer brake support.
Whoops - "revive" probably wasn't the right term; the forum was hiding the most recent posts from me. Gonna try out cFelix's wiring, as I suspect my 2022 MY is similar. We'll see if it works.
 
Whoops - "revive" probably wasn't the right term; the forum was hiding the most recent posts from me. Gonna try out cFelix's wiring, as I suspect my 2022 MY is similar. We'll see if it works.
Nevermind. Can confirm - the stock trailer wiring molex plug is completely dead in 2022 Model Ys that shipped without the tow package. No voltage on any connectors - the only wires that are connected are the grounds (two black corner connectors). Guess I'll have to live with a 4-pin trailer plug and inertia-based trailer brakes. Thanks NaperY for the service bulletin info - I should've listened.
 
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I purchased a Model Y Performance in June of last year and opted ot not have the trailer package installed. A year later I've come to realize how useful it would be to tow a trailer with my Y, so I spent some time scraping this site and others on guidance in building a trailering harness that uses the OEM connector under the bumper cover. While for sure you can go buy a Curt harness kit and clip it to your lights, run power etc... I wanted a cleaner solution.

Kudos to gman99 who got me started down the right path on finding a connector that will fit on the existing trailer harness connector installed on all(?) Model Y's.

To build the connector you will need:
- 1X Molex Connector (Male) Part Number: 34986-1601
- 7X Molex Automotive Connector Pins (Male) Part Number: 31296-0008
- Some Molex automotive crimping tool
- 16 gauge wire

Here are the application notes from Molex explaining assembly of the connector: https://www.molex.com/pdm_docs/as/AS-33472-100-001.pdf

And the pinout for the tesla connector is:

- Black (corner): Unknown
- White: Ground
- Not Used
- Red: Brake Lights
- Blue: Unknown
- Not Used
- Not Used
- Red (corner): 13V Supply
- Purple (corner): Unknown
- Black: Unknown
- Not Used
- White: Reverse Lights
- Brown: Running Lights
- Purple: Passenger's Blinker
- Green: Driver's Blinker
- Blue (corner): Unknown

The pinout for a standard 4 or 7 pin trailer hitch is easy to get from google or whatever connector you end up buying. I went with this: https://www.amazon.com/gp/product/B07YZ16N5D/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

Slap together both connectors (male tesla connector + 7 or 4 pin universal trailer harness) and you have a working Trailer harness. Note that this likely will have limited functionality - and of course choose your gauge carefully based on the requirements of your trailer lighting. Choosing incorrectly may result in fire or something like a dead tesla...
Thanks for this wonderful post. I got my 7pin trailer harness made. On my testing I can't get +12V on the Brown: Running Lights. Are they only energized when set to Drive
Just wanted to chime in. I bought the harness for my model y and installed a week ago. While it plugs in just fine, im not receiving any voltage on break/turn signal. I contacted them for support so we'll see what's up.
Thanks @snyder for the extensive write-up. I made my own harness cable. I get Left/Right pin to power up when the car is not in park mode. The "running light is not working. The moment I switch to "D" mode. Everything stop working. So I'm wondering if this is the same issue you're seeing?
 
I purchased a Model Y Performance in June of last year and opted ot not have the trailer package installed. A year later I've come to realize how useful it would be to tow a trailer with my Y, so I spent some time scraping this site and others on guidance in building a trailering harness that uses the OEM connector under the bumper cover. While for sure you can go buy a Curt harness kit and clip it to your lights, run power etc... I wanted a cleaner solution.

Kudos to gman99 who got me started down the right path on finding a connector that will fit on the existing trailer harness connector installed on all(?) Model Y's.

To build the connector you will need:
- 1X Molex Connector (Male) Part Number: 34986-1601
- 7X Molex Automotive Connector Pins (Male) Part Number: 31296-0008
- Some Molex automotive crimping tool
- 16 gauge wire

Here are the application notes from Molex explaining assembly of the connector: https://www.molex.com/pdm_docs/as/AS-33472-100-001.pdf

And the pinout for the tesla connector is:

- Black (corner): Unknown
- White: Ground
- Not Used
- Red: Brake Lights
- Blue: Unknown
- Not Used
- Not Used
- Red (corner): 13V Supply
- Purple (corner): Unknown
- Black: Unknown
- Not Used
- White: Reverse Lights
- Brown: Running Lights
- Purple: Passenger's Blinker
- Green: Driver's Blinker
- Blue (corner): Unknown

The pinout for a standard 4 or 7 pin trailer hitch is easy to get from google or whatever connector you end up buying. I went with this: https://www.amazon.com/gp/product/B07YZ16N5D/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

Slap together both connectors (male tesla connector + 7 or 4 pin universal trailer harness) and you have a working Trailer harness. Note that this likely will have limited functionality - and of course choose your gauge carefully based on the requirements of your trailer lighting. Choosing incorrectly may result in fire or something like a dead tesla...
I found this ebay item selling the Tesla OEM wiring harness (attached photos). Looking at the pinout, looks like it's using 3 corners of the molex to tap into 12V, Brake and Running Lights. Looks like Red, Purple and Blue wires. Any idea what they are?
s-l1600.jpg
s-l1600 (1).jpg
 

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