Trailer hitch wiring; is this what I think it is?

VanIsleGuy

Active Member
Joined
Feb 18, 2019
Messages
44
Location
Nanaimo, B.C.
Tesla Owner
Model 3
Country
Country
#1
I installed a ECO hitch on my 2019 SR+ this weekend. Mostly went well, I will post another thread soon with some suggestions for others taking this on.
I wasn't planning on adding trailer wiring, as I was adding the hitch mostly for a slick bike rack install. During installation, I noticed what looks like trailer wiring already installed with a blanked out connector. Is this something new? I'm wondering if they added this with the availability of the European trailer option, or perhaps for future hitch option? Anyone played with this to see what the connections are?
mystery-wiring-jpg.27274
bumper-removed-jpg.27275
 

FogNoggin

Active Member
TOO Supporting Member
Joined
Mar 19, 2019
Messages
92
Location
Lake Katrine, NY
Tesla Owner
Model 3
Country
Country
#2
So many hidden features and equipment just waiting to be activated! Please put a meter on there to test while you have it disassembled. A 12V light bulb with a couple of wires attached would do the trick.
 

Ryefry

New Member
Joined
Jan 2, 2019
Messages
4
Location
Dallas
Tesla Owner
No
Country
Country
#3
Did your lower bumper cover have the panel cutout for the hitch as well? I wonder if this module needs to be activated via body control module and if so will the service centers be able to do it in US?
 

fritter63

Active Member
Joined
Nov 8, 2018
Messages
181
Location
Atascadero, Ca
Tesla Owner
Model 3
Country
Country
#4
I installed a ECO hitch on my 2019 SR+ this weekend. Mostly went well, I will post another thread soon with some suggestions for others taking this on.
I wasn't planning on adding trailer wiring, as I was adding the hitch mostly for a slick bike rack install. During installation, I noticed what looks like trailer wiring already installed with a blanked out connector. Is this something new? I'm wondering if they added this with the availability of the European trailer option, or perhaps for future hitch option? Anyone played with this to see what the connections are?
View attachment 27274 View attachment 27275
That plug harness doesn't look typical. I can't tell for sure, were there 4 wires there (is that a red that I see on the bottom?) ? When you remove the plug/stub, are there four connectors under there (looks like only 3 from what I can see.
 

VanIsleGuy

Active Member
Joined
Feb 18, 2019
Messages
44
Location
Nanaimo, B.C.
Tesla Owner
Model 3
Country
Country
#6
Answers to questions above:
1)I've already reassembled, but I put the connector down close to the cutout so I should be able to access it without pulling bumper again. If I get a chance and can get to it I will put a voltmeter on it.
2) No, the undertray did not already have cutout, I had to cut it. I saved the piece I cut out and added some clips to it so I can put it back in when not using hitch. I will post those details in another thread soon.
3)It is not a standard trailer connector (at least not that I'm familiar with). It only has 3 connections and is a weatherproof connector.
4) No, it is not for parking sensors. This connector is not attached to anything. Ultrasonic sensor connection was on passenger side of bumper (Can't see in picture above).
 

SalisburySam

Well-Known Member
TOO Supporting Member
Joined
Jun 6, 2018
Messages
255
Location
Salisbury, NC
Tesla Owner
Model 3
Country
Country
#8
@VanIsleGuy, very helpful post and thanks for sharing your experience with your hitch project. I look forward to seeing what Tesla does with the Model Y.
 

GDN

Moderator
Moderator
TOO Supporting Member
Joined
Oct 30, 2017
Messages
3,509
Location
Far North Dallas, TX
Tesla Owner
Model 3
Country
Country
#10
I took delivery late March in Vancouver, B.C., so I would expect late feb/early march 2019 build date. It was one of the early batches of SR+.
The tag inside the drivers door will tell you the month and year the car was built. If you ever need to get more specific you can always ask at the Service Center. They can look up your car and tell you the exact day it was built.

This might become more important to you down the road to know if you have HW 2.5 or 3.0.
 

VanIsleGuy

Active Member
Joined
Feb 18, 2019
Messages
44
Location
Nanaimo, B.C.
Tesla Owner
Model 3
Country
Country
#11
Ok, a few updates.
Used my multimeter to check plug voltages. Outside two wires are thick red and black wires, middle is yellow wire.
Before I woke car up voltage between black and red was 0 (floating), and between black and yellow was 11.9V
Once I woke car up, voltage between black and red was 13V, and between black and yellow remained the same at 11.9V.
I put my hazard lights on, and nothing seemed to change (too bad).
If it is for trailer wiring, it doesn't seem like good ol' school wire directly to lights. I'm wondering if it is some sort of canbus signal. Perhaps I will try to hook the oscilloscope up to it at work if I get a chance this week.

Here are some closeups of the connector (this is the removable cap):
cap1-jpg.27310
cap2-jpg.27311
cap3-jpg.27312

This is the female end wired to the car (where I took my measurements):
car-side-female-jpg.27313


I also took a picture of the decal on my door sill. Does this mean March 2019 or third day of 2019?
doorsill-plate-jpg.27314


If there is anything else besides hooking this up to an oscilloscope that people want me to try let me know. I've routed the connector down to the hole I cut in the cover under the car where the hitch comes through so it is relatively easy to access.
 

JasonF

Top-Contributor
Joined
Oct 26, 2018
Messages
850
Location
Orlando FL
Tesla Owner
Model 3
Country
Country
#12
If there is anything else besides hooking this up to an oscilloscope that people want me to try let me know. I've routed the connector down to the hole I cut in the cover under the car where the hitch comes through so it is relatively easy to access.
I found this:
 

JasonF

Top-Contributor
Joined
Oct 26, 2018
Messages
850
Location
Orlando FL
Tesla Owner
Model 3
Country
Country
#14
That install is amateur (and that's the PC version of what I'm thinking). I'll wait for the Tesla solution.
I posted that video in a hurry (first search match), but watching it now, I'm concerned that the taillights are supposed to be PCM controlled (according to a teardown I saw), which potentially means two things: 1) the wiring to the taillight might not be able to handle the amps of trailer lights; and 2) putting that much resistance on the circuit might harm the PCM controller or the light controllers.
 

D. J.

Active Member
Joined
Apr 10, 2016
Messages
33
Location
Boulder County, CO
#15
@JasonF - the unit in the eTrailer video uses ZCI (Zero Contact Interface) monitors around the PCM-controlled taillight wires - so it senses current flowing through turn signal, brake, and running light wires. Those signals are transmitted (low-voltage/low-current, likely TTL or tinier) to the black box that is supplied with its own dedicated ground and 12V wire that has to be routed all the way to the battery. That 12V feed directly from the battery goes into the black box relays and is what supplies the actual trailer wires through the 4-pin connector.

So if something shorts out on the trailer wiring, the worst case is that the black box gets fried or (ideally) the fuse between the battery and the 12V wire blows.

All in all it looks like a pretty safe system. I've been running an older style "opto-isolator" system on my old Land Cruiser for a decade now - similar idea but did require tapping into the taillight wires rather than the ZCI adapters (but about 1/3 the price) but it still used a dedicated 12V line from the battery to the black box - it's been rock solid even when plugged into weird rental trailers and partially functional boat trailers.

Ordered one today and will install sometime later this month - will post when I know more. I'm not super-optimistic about the timeline of an official Tesla trailer retrofit kit for 2018 or older Model 3's.
 

fritter63

Active Member
Joined
Nov 8, 2018
Messages
181
Location
Atascadero, Ca
Tesla Owner
Model 3
Country
Country
#16
@JasonF -
I'm not super-optimistic about the timeline of an official Tesla trailer retrofit kit for 2018 or older Model 3's.
Fallback plan: You can rent a truck with an 8 foot bed from UHaul for $20/day... :)

And you avoid the (was it $600?) registration fee tax for "heavy vehicle road wear and tear" that I was paying for something that sat in the barn 99% of the time. :)
 

TrevP

TOO Founder / Administrator
Founder
Joined
Oct 20, 2015
Messages
6,722
Location
Toronto
Tesla Owner
Model 3
Country
Country
#17
Did your lower bumper cover have the panel cutout for the hitch as well? I wonder if this module needs to be activated via body control module and if so will the service centers be able to do it in US?
Looks like Performance Model 3s built since about April 2019 have the hitch cover in place.

ljhcyha-jpg.28333
hy9furp-jpg.28332
 

Judd

New Member
Joined
Aug 20, 2019
Messages
1
Location
Florida
Tesla Owner
Model 3
Country
Country
#18
There is a Norwegian page that has excerpts of some Tesla schematics showing what looks like the wiring around this connector.

https://www.tocn.no/2019/01/kommer-tesla-endelig-med-hengerfeste-pa-model-3/

You can use Google Translate to read the text, but there are two significant things in my eyes - it mentions "high-side drive" which is the type of drive that would be required to drive conventional trailer lighting systems and also lists LIN connections, which is likely a Local Interconnect Network connection, a digital signaling standard used to control relatively simple things (like trailer lights) where a typical CAN bus connection is overkill. LIN bus is typically three wires - power, ground and a bidirectional data line, no doubt the yellow wire found above.

If this is correct (and as the Norwegian diagram seems to indicate) there is probably another module that is the actual trailer lights interface that converts LIN bus trailer light signals to switched voltages for the trailer lights. It may also pass data in the reverse direction to adapt vehicle dynamic stability when actually towing a trailer (this is my conjecture).

There's still a lot of missing pieces here, but I hope this means a Tesla owner might be able to purchase the missing Trailer Light Controller from Tesla (X034 ?) and have a factory designed trailer lighting setup. Still a little more data gathering to be done, and of course there's no guarantee it isn't locked out in software somewhere.