Wiring requirements to satisfy Tundra tow package trailer detection?

I'm rewiring a dual axel 16' landscape trailer from scratch and can't seem to get my 2020 tundra with tow package to 'see' the trailer. When I plug my other dual axel trailer in I get immediate conformation (the green trailer icon) and am able to manipulate the brakes with the manual slide.

I'm trying to figure out what makes the tow package trigger to recognize it's attached to a trailer and work the brakes.

I've got a 7 blade connector going to a 7 way junction box. Running lights work, tail lights and blinkers work. I am trying to run one 12V power (blue wire) plus ground back to each axel so the circuits are not dependent on each other in case of a loose connection the other axel would still function.

On each axel I've run a power and ground across the axel from the far side. From my understanding polarity doesn't matter when connecting to the electromagnet. Then I connect that line to the other brake, then connect the lines that run up to the junction box (making sure to keep ground connected to ground and power to power.

No matter what I do I cannot get the Tundra to see the trailer. I did find last night that I may have a bad electromagnet on one side, but even when I do not include that axle, still no trailer shows up.

Another issue I have is that this trailer has no rear running lights, but I thought the rear combo brake / blinker should have a running light no? As is right now at night someone would run into the trailer because to rear running lights. I bought it this way and it doesn't appear to ever have any.

Any ideas on what the Tundra needs to see the trailer?

Thanks!

 

First thing I'd do is get some marker/tail lights going. Might just be bad bulbs. If bulb filaments and contacts look good, check the wiring. Never know, previous owners maybe only used the trailer in daylight. Not sure why your post says running lights work, but then later says they don't work.

 

After searching around a bit I'm pretty sure the combo brake / tail lights that are on there are also supposed to function as running lights. The side running lights work, but no tail lights. Ill check the bulbs tonight (although I think they may be LED) Also, if the brakes and blinkers work, isn't that the same bulb as the tail light bulb?

So you think this issue could be causing no trailer to be detected, rather than the brakes?

 

If LED they will be a different LED. If not LED it will be a twin filament bulb that will have two hot contact dots on the bottom of the base one brake turn one for tail. Not exactly sure how the truck identifies a trailer is hitched up. Maybe it knows by brake light current draw when you step on the brake. Maybe not. I can't really confidently answer without more research. Sorry.

 

One thing I just thought of is that there is only two wires on these combo brake / tail lights. I just looked at a pair online and there are three wires. Does that mean the lights I have are only setup for braking and turn signal? Thanks!

 

Depends on if the mounting bolts are the ground source.

 

Ahh! Good call. I think you just saved me a bunch of time and money. Was about to go buy new lights and extra wire. I may be able to get tail lights working tonight just by moving the "ground" to the running light pin. (if the mounting bolts are ground) Thanks!

 

Turns out the mounting bolts were the ground. The lights are not LED. The bulbs have two filaments each. I was able to quickly move the wire from the ground terminal to the running light terminal and instantly had tail lights.

As far as the brakes go.. Looks like the brake controller is expecting to see all 4 axles wired up. Testing with a 12V battery and volt meter showed an issue with one of the brakes. I took it apart and found the wire sliced right before it went into the magnet. After repairing the slice and hooking everything back up the brake controller recognized the trailer and I was able to manipulate the gain and all that.

Thanks so much for the help!