dmort

To add another twist to the issues with Fords design to only energize the trailer charging pin when the computer recognizes that a trailer has been connected via brake activation is that when a electric trailer lift jack (which now come with 7 pin connector plug to energize the trailer lift) is installed on the trailer, the truck will not be able to power the installed lift. It would be more beneficial if the truck recognized a being in an " under load" condition to activate the pin then accessory devices can be utilized with the truck.

CeeDee

I too have had other owners complain of this issue with their new F-150s. I honestly don't know why Ford did this. Most likely to pad the bottom-line, cut corners and makes things cheaper. It's misleading when they dress it up as being plug-n-play, high-tech and "smart."

After spending almost an hour reading through these posts, Here's a couple of questions...

What happens if someone has just a small utility trailer or even a small boat trailer with no brakes on it. And say this small trailer has a small battery on it to power a motorized tongue jack... is this person pretty much screwed and going to end up with a dead trailer battery because the truck won't see want it wants to see?

If indeed the "smart trailer connector" is looking for the trailer brakes before providing power to the accessory (charge wire) on the trailer connector, then what exactly is it looking for?

I don't have a trailer of any sort at the moment, let alone one with brakes. What is the open circuit resistance of the brake wire on the trailer side? Is it looking for a certain resistance value perhaps?

Is there a way we can make it "see" what it needs to see, to give us what we want?

Feathermerchant

I think it needs to see the electric brakes on the trailer. Then it energizes the 'charge' wire. But on the latest generation, the current available is very small. That is why some have run their own circuit and relay so that any time the ignition is on, the wire is hot and capable of 20A or so.

Gordy49913

Wiring diagrams for the trailer circuits show the battery charge wire as a #16 wire.
I would also venture to guess the brake wire does detect the trailer. Note here in the TBM wakeup on how when not braking the TBM is sending a voltage pulse to the trailer every 4 seconds to make sure a trailer exists.
I could not find anything related to the trailer module itself.
For information according to the wiring book, if you have a 7 pin trailer connector, it is controlled by the Trailer Tow module which is under the dash above the drivers feet. Plus you need the Trailer Brake Module if you have electric brakes. Both of these modules are hooked to the trucks network. The fuses/relays for all this are under the hood of the truck.
The brake wire happens to be a #12.

TBM Wake Up
NOTE: These conditions require that a trailer not be connected to the trailer tow connector.
The following conditions describe the normal operation of the TBM at start up.
When the ignition is set to the ON position and the manual lever is set all the way to the left with a gain of 10,
the message center should display TRAILER DISCONNECTED. At the same time, with the vehicle stationary, battery voltage should be present at pin 3 of trailer tow connector C4099.
When not braking the TBM sends a voltage pulse every 4 seconds to pin 3 of the trailer tow connector to determine if a trailer is connected to the trailer tow connector.

CeeDee

Sounds like the mystery and possibly the key is within the TTM (trailer tow module). I do not have a TBM. And I'm betting the TBM doesn't have the final say when the charge wire kicks on or off. My truck didn't come with a TBM. I have a nice little pocket instead, that doesn't hold anything very well. But I do have the "tow package." I was okay with that when I got the truck since I knew I wouldn't be towing very often if at all. But I should be able to have the charge wire work on my trailer connector to charge my trailer battery (if I had one).

I really wish Ford had a good technical support department. Not just, "refer to your local dealer." When it comes to stuff like this, most have no clue what I'm talking about and think I'm nuts.

Gordy49913

Easy test for the ones with a brake module, hook some kind of load to the brake wire to simulate trailer brakes, see if the Battery wire becomes hot. That way you don't have trailer lights involved. I have to buy a 7 pin plug to play around with. Then have to find a big enough load, from what I see brakes are over 3.5 amps or there about.
I have no idea how it would work with out the TBM.
I'll have to try Forscan tomorrow and see if those modules show.

Sawdust102

In reading through this issue and other post, and testing my own. I have yet to get power to the trailer.

In reading, my understanding is not only does it need to detect a trailer, but also something there to charge. So on my trailer, with tbm and trailer hooked up (with brakes) the power wire was still not energized, I believe because my battery was at 12.1v. So the truck would still not turn on the power because it felt it was not needed.
But like most info, this is just a guess as to what is going on.

Feathermerchant

Didn't someone here post that you had to have the truck in drive also?

CeeDee

I believe you need to assign the trailer in the driver's gauge menu. Give it a name and assign it (turn it on). You can N/A all the pro-trailer stuff. Then with the trailer plug connected to the truck you should be able to start the truck, and press the brake and it should see it. Something should show in the gauge menu that the trailer is connected somewhere within those steps. Then, maybe test that charge wire.

I'm only restated what I've read on how it's supposed to work and playing with other F150s. I do not have a trailer of my own to test this.

doimec

Guys found this bit of information for 2016 / 2017 manual on page 280 / 281.

ESSENTIAL TOWING CHECKS
Color - Function
Yellow - Left turn signal and stop lamp
White - Ground (-)
Blue - Electric brakes
Green - Right turn signal and stop lamp
Orange - Battery (+)*
Brown - Running lights
Grey - Reverse lights
*Your vehicle must recognize the trailer before the trailer can receive power.

2017 Ford F150 Owners Manual