Solved- DD lights cause "Trailer Detected" message

[Whaler27]

I did contact them. There is not a harness available for the LED equipped trucks. The root of the issue is the way the trucks with LED lighting detect a trailer. Trailer lighting is controlled by a FET circuit. Essentially, anything that puts a load on the brake/ reverse/ trailer brake circuit results in a trailer detected. even my little ATV trailer with a 4 pin connector trips the trailer detection. It seems the running lights are low power and do not trigger the truck. They are .06 amps for the pair.
That said, I'm going to use the CHMSL customer access wire for the brake function. The reverse function/ flood I'm going to try using a relay for. The realy coil draws about .18 amps. Hopefully this will be low enough that it won't trip a trailer.
It'll be a couple weeks before I can Uninstall the harness and rewire it with the relay. Then I'll tie it all up under the truck and test drive before I route the wiring. Lol. I should have done that the first go round.

My Offroad Alliance wiring harness for my backup lights (S2-pros) was designed to pull power from the reverse wire on pre Canbus trucks. Since I have a 2024 truck, there wasn’t a single reverse power wire to tap into behind the taillight, so I used the reverse wire from the wire loom to the trailer plug. Now, when I put the truck in reverse my backup lights come on. The harness also allows me to switch the lights on using one of my upfitter switches. The trailer notification doesn’t come on when I put the truck in reverse — so either the load isn’t sufficient to trigger the notification, or the system isn’t looking for load on the reverse wire.

 

[The Evil Twin]

My Offroad Alliance wiring harness for my backup lights (S2-pros) was designed to pull power from the reverse wire on pre Canbus trucks. Since I have a 2024 truck, there wasn’t a single reverse power wire to behind the taillight, so I tapped into the reverse wire from the wire loom to the trailer plug. Now, when I put the truck in reverse my backup lights come on. The harness also allows me to switch the lights on using a one of my upfitter switches. The trailer notification doesn’t come on when I put the truck in reverse — so either the load isn’t sufficient to trigger the notification, or the system isn’t looking for load on the reverse wire.

Got a link for that harness? I wasn't able to find it on their website.
With my lights having marker and brake functions, it complicates things a bit. That's why I plan on waiting for a long weekend un a couple weeks to tear into it

 

[HelmPilot]

I’m also interested in how you did this for auto lights with reverse gear selection and also wired an upfitter switch. I think I have a similar harness adapter off the 7 pin trailer connector but that doesn’t include a way to do it with the upfitter switch unless you run a whole new feed wire from the upfitter switch. This is the harness I have it’s from Baja Designs part # 60-0068.

 

[Terryw123]

This is the company that makes the harnesses for off-road alliance. It’s been a minute but I believe his name is John. He literally will make you any harness you want. He helped me do some pretty cool stuff so I could run my reverse lights when I was in reverse but also tie it to my SWARF works 3rd brake light S2. It’s kind of weird to describe but the reverse lights work while in reverse while the truck is turned off because it’s wired also to aux number 6. That also activates the cargo light from my third brake light, which is an S2 pro. I can also turn on just that S2 pro by hitting the cargo light. I hope that makes sense. John is awesome. He literally called me 11 o’clock at night and helped me work through the entire process. I literally can’t say enough good stuff about that company.

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[Whaler27]

Got a link for that harness? I wasn't able to find it on their website.
With my lights having marker and brake functions, it complicates things a bit. That's why I plan on waiting for a long weekend un a couple weeks to tear into it

The Offroad Alliance website is terrible. Even when I know they sell a particular part it takes me ten minutes of imaginative guessing and clicking to find it. Their service is great — very nice, knowledgeable people — but they need a website redesign.


Here’s the link:

Wiring harness

 

[Whaler27]

I’m also interested in how you did this for auto lights with reverse gear selection and also wired an upfitter switch. I think I have a similar harness adapter off the 7 pin trailer connector but that doesn’t include a way to do it with the upfitter switch unless you run a whole new feed wire from the upfitter switch. This is the harness I have it’s from Baja Designs part # 60-0068.

As explained above, I did it by buying and installing the wiring harness linked above. On pre CANbus trucks the installation is idiot-proof. Just follow the directions and feed the white wire up to the back of the taillight to tap into the reverse wire. That takes about two minutes, including the time to remove and replace the taillight, but the taillight tap doesn’t work on the newest trucks, because there isn’t a single reverse-light wire in the taillight harness, so you have to find another solution to power the lights. My solution was to cut into the harness entering the trailer plug, tap into that reverse wire, and seal it all back up.

I assume the Offroad Alliance harness has an inline resistor that prevents power from running back to the upfitter switch when the truck is put in reverse, but I don’t know. Maybe that’s not necessary? Either way, it works great, as it did on my Raptor for over six years.

 

[The Evil Twin]

My solution was to cut into the harness entering the trailer plug, tap into that reverse wire, and seal it all back up.

I assume the Offroad Alliance harness has an inline resistor that prevents power from running back to the upfitter switch when the truck is put in reverse, but I don’t know. Maybe that’s not necessary? .

That first part is good Intel. That tells me there is something in the DD harness that trips the trailer switch in reverse. It's not just the lights. Their harness does tap the trailer reverse pin.
Regarding a diode (those allow flow one way) for adding an upfitter override; it is not needed. The power is DC from the same source. The upfitter is an open circuit when turned off (no flow can go back through it. If the switch is on when you shift into reverse, it's fed the same power from 2 wires. Think of hooking a light direct to a battery. One positive wire and one negative wire. The light turns on. Now add a 2nd positive wire. Same source/ same load.
Additional fuses aren't needed either. The trailer reverse light fuse will protect the trailer wire and the wire back up to the upfitter relay. The upfitter fuse will do the reverse. Just use the appropriate wire and fuse size for both.
Hope that made sense.

 

[Whaler27]

That first part is good Intel. That tells me there is something in the DD harness that trips the trailer switch in reverse. It's not just the lights. Their harness does tap the trailer reverse pin.
Regarding a diode (those allow flow one way) for adding an upfitter override; it is not needed. The power is DC from the same source. The upfitter is an open circuit when turned off (no flow can go back through it. If the switch is on when you shift into reverse, it's fed the same power from 2 wires. Think of hooking a light direct to a battery. One positive wire and one negative wire. The light turns on. Now add a 2nd positive wire. Same source/ same load.
Additional fuses aren't needed either. The trailer reverse light fuse will protect the trailer wire and the wire back up to the upfitter relay. The upfitter fuse will do the reverse. Just use the appropriate wire and fuse size for both.
Hope that made sense.

This is helpful.

My interaction with electricity is a little like our dog’s reaction to the vacuum cleaner: I want to master it, but it still scares me, because I don’t really understand it.

 

[Slippers]

I'm also using the Baja Designs 60-0068 combined with an upfitter to power my rear facing S2 pods so they come on in reverse or when I flip the upfitter switch. 24 lariat, so I don't have the LED tails.

 

[Canyon Trekker]

I haven't experimented on the truck's connector yet, but there are likely several ways that the truck can sense a trailer. Since there are 4 pin, 5 pin, 7 pin, 13 pin, etc. trailer connectors, the truck will likely be designed to use different method of detection since they don't know what type of trailer you are hooking up. But in all cases, the trailer has to be "seen". It's hard to find a source that covers all of the scenarios but here is what makes sense for connecting back-up lights without triggering the trailer detect.

The seven-pin connector likely has a couple of trailer sensing conditions depending on the type of trailer attached. The trailer attached signal may be from an "sensed" excess pull on the running lights, a sense line on pin 2 (blue wire) for electric brakes, or possibly "logic" from the taillight proximity sensor. (Since you can define how long the trailer is in the software.) It may have 4, 5, or 7 pins on the connections to match the trucks connectors.

It seems to me that if you use the center pin of the 7-pin connector to trigger or hook up the lights direct, no trailer would be sensed since there is no power here until you put the truck in reverse. So, for hooking up lights without triggering the trailer sensors, use the center pin (yellow on most harness') to energize the lights. The wire color on the truck will likely be Yellow/blue and will be a heavier gauge than the running and brake light wires.

This pin is usually used to trigger a lockout of the reverse solenoid in a conventional trailer with surge brakes and possibly a reverse light on the trailer. And again, since the truck doesn't know what kind of load will be on this pin, it is likely not a sensing wire.

The second scenario will be hooking up a heavy load such as the DD lights without triggering the trailer sense flag. In this case, using a relay to be triggered by the center pin (Yellow or Yellow/blue wire) and using the 12 Volt hot connector (Pin 4, likely black; 12 gauge) to power the lights, shouldn't trigger a trailer detect. However, if it does, you may need to run a direct fused wire from the battery to drive the lights through the relay pins.

The pin numbers are more important than the wire colors. The pins would be standard; wire colors can vary from manufacturer to manufacturer.

Here's a good video from E-Trailer for a description of the wires to connect to and the pins associated.

Here's a diagram off an Amazon product to show the pinout of the 7-pin connector.

 

[The Evil Twin]

That's sort of what I intend to toy with next weekend. Either a micro relay or FET relay. One of those should solve the reverse lighting.
The running / brake lights are a different animal. From some research, the LED equipped trucks use a 'trailer tow module' for lighting. I suspect this is a solid state device that communicates over the bus to the BCM or ECM or whateverCM and says there is a trailer.
I like the idea of extra rear marker lights because I travel very rural areas. Added brake lights are a plus.

 

[The Evil Twin]

Update!
Dissected the DD harness yesterday. Removed the little brake strobe box and the brake light lead from the harness.
Taped up the bare wires and half ass reinstalled the harness today. I took her for a test drive and the results are......
<suspenseful music plays>
Lighting off: no trailer/ all nanny sensors on.
Lighting on: DD running lights on and no trailer/ all nanny sensors on.
Lighting auto in daylight: no trailer/ all nanny sensors on.
Lighting auto at night: DD running lights on and no trailer/ all nanny sensors on.

Did some research and found that there is a CHMSL lead at the rear of the truck. It's for topper/ utility body use. I'm figuring I can tap into that wire for the brake light function on the DD lights. We shall see!
I have to take the truck in for her PPF touch up, so it'll be next weekend before I can test that. I should probably tap DD tech support to make sure the high power red and low power red can be energized simultaneously. I don't know the circuitry in that black box that I removed. So it may have "turned off" low power when the brakes are applied. Dunno. They have been super helpful with my nagging questions so far.

 

[The Evil Twin]

Shits gonna get real tomorrow! Imma show this truck and its smarty pants electronics what's up!

 

[The Evil Twin]

I’m also interested in how you did this for auto lights with reverse gear selection and also wired an upfitter switch. I think I have a similar harness adapter off the 7 pin trailer connector but that doesn’t include a way to do it with the upfitter switch unless you run a whole new feed wire from the upfitter switch. This is the harness I have it’s from Baja Designs part # 60-0068.

I'll have to draw a diagram once I complete this silly project. If your harness only powers floods, it's pretty easy. You will have to run a lead from the upfitter box under the hood back to the rear bumper. Then you just T tap the center pin wire that goes to your lights. I couldn't make out the wire color in your photo. I recommend using 14 gauge wire and changing the fuse size to match the trailer reverse circuit fuse. When the upfitter is on, you'll be energizing the reverse circuit wire too. So to protect the wiring, you want to size the fuse appropriately. No diodes or relays needed.
FWIW, run an extra wire or two and just cap them off. Never know what else you want to power back there in the future.

 

[The Evil Twin]

Getting there!

 

[Apples]

^ ^ ^ Very happy to hear this seems to be working out for you.

This is an invaluable thread! especially since I have yet to wire the first two circuits of my truck's Upfitter system.

I have already (two years ago) on my little squaredrop trailer run a reverse lights wire all the way to the rear of the trailer so that I could (this is all before any Super Duty) power white reverse lights at the very back of the little trailer, those being some Sylvania flush-mount LED.

I had planned to use the trailer's house battery bank to power the reverse lights and use the reverse light wire from the 7-pin trailer wire harness as the signal to switch a Bosch automotive 5-pin relay. Then, with a toggle at the back of the trailer, simply switch on the lights as loading lights, or courtesty lights, etc... but now! I may do this from the cab of the truck! via the Upfitters.

It's all related, see! and I cannot thank all the participants in this thread for their experienced, helpful replies. This is a project for the coming months. Cheers!

 

[The Evil Twin]

Success! All functions work and no trailer.

 

[Apples]

Edit:

It's working, now!

Looking good! Winthorp.

 

[Apples]

Guess what.

I thought this would be a cool thing to do/have, but I was mistaken...

It's REALLY REALLY cool. Works as described, but then some.

This I must do to mine but it has to wait a few months.

 

[The Evil Twin]

Now, if only we could get that little vid to woik.

*grin*

Might be on my end, though.

It's a fairly compressed mp4. I just tried in Chrome without being logged in and it worked.
The next part of the project (later on) will br the flood light override from an upfitter. I ordered a manual and want to trace out the trailer reverse circuit. I'm not sure if it runs through a FET or not. My knowledge in that area isn't very deep, but I don't think backfeeding them is OK or not. Maybe @Canyon Trekker can shed some light on FETs and reverse flow?