7 pin trailer connector wiring
 

I cannot figure out how my 7 pin connector is wired because it's not making sense to me. I have a picture of the wires connected to it underneath the bumper, looking straight up. When I translate that to the view from behind the truck looking at the connector, the colors should be as follows. (Note the flat part is at the bottom of the connector not the top.)

Therefore, translating to the view from the back of the truck, beginning at 12 o'clock:
1 white
3 yellow
5 brown
7 orange
9 green
11 blue
Center: grey

Now I'll give voltages based on position and not color (with truck off):
5 hot 11 (ground?) voltage 6
9 11 voltage 6+
1 11 voltage 6
everything else zero voltage

With truck on:
5 hot 11 (ground?) voltage 9
9 11 voltage 9+
1 11 voltage 9
everything else zero voltage

With truck on and light on:
5 hot 11 (ground?) voltage 12+
9 11 voltage 12+
1 11 voltage 12+

With truck on and either turn signal on:
no change

This was a fleet truck. It's not making sense.

https://cimg6.ibsrv.net/gimg/www.f15...b01c83521.jpeg
https://cimg8.ibsrv.net/gimg/www.f15...56ba68626.jpeg

Based on the picture from under the truck, this is how the wiring should be when looking at the connector from the back of the truck.


https://cimg6.ibsrv.net/gimg/www.f15...51450c4925.jpg
Translating to view from back of truck

On the snap cover is the legend for what each contact powers. I'm presuming this is a late model F150 2015+? If you don't have a trailer connected trying to measure voltages at the jack will be an exercise in futility with late model F150s

Thanks MikeD134. Yes there's a diagram there.

The second part doesn't make sense to me. If I hook up a trailer (and I will but I need to test before then) and something doesn't work, how do I test to find out if it's the truck or the trailer? There must be a way to test the truck.

You can buy truck end trailer light testers for four and 7 way plugs at local auto parts places amazon etc.

Trailers are best tested on another truck with known good wiring. I always suspect the trailer has the problems especially if bought used. Who knows what ham fisted Prior Owner Stupidity kept it on the road.

Thanks henfield. I think I'll do that. I retested today knowing the diagram and it still doesn't make sense and some things don't work.

Something tells me the truck had its rear bumper replaced but the guy screwed up the truck side of the trailer connector. wires seem to be going into the wrong position.

Seven way connection

So you plugged in a 7 pin trailer and lights don't work? Or you just chasing your tail trying to check the plug without a trailer? The truck doesn't send power unless it "sees" a trailer.

The truck has a Code: U0137 - Lost Communication With Trailer Brake Control Module, Code: U0252 - Lost Communication With Lighting Control Module- Rear 'B', and Code: U0553 - Invalid Data Received From Lighting Control Module-Rear 'A'.

It could have nothing to do with any of these, but just the presence of them makes me think it is quite possible someone messed up the 7 pin.

When I push the TBC module slider the dash shows "no trailer attached" so I know there is at least some communication with the TBC. I'll be getting all this worked on.

Thanks for the link.

There are three different wiring schemes for wiring a 7 way trailer plug, if someone has previously owned the truck, they may have changed the wiring to suit their needs. There is the 7 way traditional, the 7 way RV Standard, and the 7 way heavy duty. If you go to www.etrailer.com/faq-wiring, you will see a page with photos of the different wiring schemes.