BigJohnLew

Hey all.
My 2021 only has 4 wires feeding the 7-pin connector. I purchased the Trailer Backup Camera and Trailer TPMS system, but my truck is not recognizing them. I'm trying to see if I can update the wiring harness from the 4 wires to all 7. I was searching for the part, but did not find it. Anyone have any info.
Much appreciated!!!!

Thanks,
John

fiver

See Any update on a Trailer TPMS system? | F150gen14.com -- 2021+ Ford F-150, Tremor, Raptor Forum (14th Gen) | Owners, News, Discussions

All is answered there.

For me, harness ML3Z-13A576-TFA provided all the wires to fully-populate both the 7-pin and 12-pin connectors (the 12-pin connector being the one for trailer TPMS and cam support) and I now have both fully operational.

Good Luck, Have Fun!

BigJohnLew

Hi @fiver ,
Thanks for sharing the link to that harness. Did you get any documentation on how to swap out the old harness? Was that a difficult process?

thanks,
John

fiver

With rare exception Ford replacement parts (different from accessories) don't come with documentation; this harness does not.

Here's my 3 posts with pics which may be helpful. Note my project included extension of the connector to inside the bed for my 5th wheel trailer, you can just ignore that part.

first post with project goals

second post with pics of the harness needing replacement

Final post with more pics and descriptions

Difficulty is in the eye of the beholder, I have no idea about your skillsets, tools, or work habits. For me not difficult, but I've been wrenching on cars for 60+ years. I just carefully worked through the process, paying attention, taking a few pics before removing things, and thinking as I worked. A set of steel 'trim popper tools' is most helpful. this is what I use (there's lots of R&R of harness 'christmas tree' fasteners pressed into holes in the chassis, some in awkward locations, those tools make that easy).

I suggest you take the time to read through the long thread I linked - it's a wealth of useful info and easy / quick to skip the obviously non-substantive posts.

BTW, have you already confirmed that your IPC has the menu item for trailer TPMS? Does your 360-degree cam display have the aux button? Not all early 2021 builds do, and if you don't you are also looking at some FORScan programming described in that thread.

Good Luck, Have Fun!

BigJohnLew

Yes, my instrument cluster does have the display for Trailer PMS (currently says nothing detected). My display also has the Aux button.
Based on your posts and other research, it does seem that I need to order the ML3Z-13A576-TFA wiring harness and this should work.

Thanks! I'll update when I get it done!

BigJohnLew

Hey @fiver
I went through and swapped out the wiring harness. It was a bit difficult due to all the tight locations, but I got it done.
here's the interesting part. My truck now shows my trailer backup camera. However, my truck says no trailer is detected. For a few moments, my truck also let me setup the Trailer TPMS, but that has since disappeared. Any thoughts on how some things might not be recognized? I tried to double-check all the connections and everything seems good. My truck even once said the Trailer was connected but only had the running lights, no brake or turn signals.
any help / thoughts, would be greatly appreciated!!

Thanks,
John

fiver

I've not encountered similar issues, have no suggestions beyond confirming all the circuits on both the truck and trailer.

Good Luck !

EDIT - IIRC some early trucks have a recall or TSB relating to the Trailer Module, you might try to see if yours is subject to that (?)

BigJohnLew

I'll have to check the connections. I had no issues with the trailer connection prior to swapping the harness. I guess there is a chance that the new harness has a fault.


Thanks!

BigJohnLew

Update.
I found 3 bad fuses: #56 Trailer Stop and Turn. #91 Trailer Tow Light. #107 Towing Battery.
Once I replaced these, the new harness works! I now have the Trailer TPMS and Trailer Backup camera!!

So, glad this worked!!!

This is the wiring harness that I ordered from TASCA parts: ML3Z-13A576-TFA (About $92)
This is the Trailer TPMS and backup camera kit that I ordered from Ford: FOML3Z-1A189-F: Kit - TPMS Sensor (About $1400)

Good luck all,
John