One high beam not working - 2019 Tundra

Nope. The bumper was a simple swap. The only change that may be related to this problem is the installation of the fog lights in the new bumper and the "box" that is co-located with the fog lights. The blue wire (high beam positive) from the headlight socket runs down to this box.

FYI, this is the box I'm referring to.

 

There is nothing in the wiring diagrams that connects the high bean wire to anything for the fog lights.
I think the ECU turns off the fogs with the hi beams (some of us have done a bypass for always-on fogs) but there is no BOX with a HI beam wire connecting the fog lights.
I think you are narrowing this down..

Open it up and see what is in there, maybe a fuse or a relay.
Whatever is in it, disconnect it and see if your issues goes away.
This might be what is grounding the hi beam.
That box looks like some aftermarket stuff..

Are these aftermarket fogs or OEM?
Is there a box on both left and right fogs, or just the one side?

Did you buy this truck new or used?
I might have missed that in previous posts.


I will not rest until this is figured out...

 

I’d look in the box if that’s aftermarket. Generally your high beams interrupt the fog lights. Maybe that box is aftermarket and does all that in there. Worth looking.

 

Ok, so that box is not wired into the fog lights. It's just co-located with them. On the stock bumper there was a mounting spot near the fog lights. With the new bumper, that box is simply zip-tied onto of the mounting points of the fog lights. Here's a look inside. When I Google the p/n on the relay it comes up as a DRL relay.

 

And here's the relay. Filled with muck... With the relay removed, I lose both high and low at the left headlight. All other lights remain functional (including DRL).

 

WTH !!

 

So.... yeah. That was the problem.... With the cow-catcher replacement bumper you lose the splash guard and front fender liners. This box, whatever it is, has a small unsealed hole where the wires enter. A few months of driving in sloppy east Texas weather eventually allowed that thing to fill up with muck... I'll seal that wire path with some RTV.

 

So you got it fixed?
I can rest comfortably now?

I don't understand the connection between the headlights and DRLs..
The schematic is confusing since it shows an LED headlight connection in conjunction with halogen headlights.
But even with that, there is not a separate relay for left and right anything...

I hope you got it figured out so I can sleep all night tonight...

Again, welcome to the forum...

 

Yeah. It's fixed... There isn't a connection between the headlights and fog lights. It just appeared that way at first because that box (whatever it is) is mounted to the same post as the fog lights on the bumper and it looked like the wires passed through... I couldn't find that relay on the wiring diagram either, but I also couldn't read it very well because it was unreadable when I zoomed in.. I figured maybe the relay was on the diagram but I just couldn't locate it. Either way, I now have TWO high beams for the first time in months. I'll relocate that box to get it further away from splashing and seal the little hole where the wires enter with some RTV. Thanks for all of your help!

 

So I found this thread and I am having the exact same problem! Drivers side...I have a different bumper, etc! Did you get a new relay? Did you get from Toyota or like a local parts store? I want to have something ready when I take the front apart! Thanks!

 

Is that box from the “fix” for the high beams burning up the wire harness? Is that why it’s not on the wiring schematics?

 

the harness is fine. And no problems since replacing the replay and relocating the box. I’m guessing that it was located near the fog lights because it would also house a relay for the front parking sensors (which my truck is not equipped with).

 

I do think that is the "fix" and why it is not on the diagram...but I am no expert...I got to mine and there was water in the box and the relay switch was rusted...changed with a new one and problem fixed! I remounted it with some electrical tape covering the hole in the box.

 

It totally is the box… Comparing the pics in post 34 above it has the same flange to attach to the stock bumper as this post shows: https://www.tundras.com/threads/headlight-issue.118670/#post-3047897
Those pictures show it at an interesting angle but with the lid up and would run water away from the connection. How long has yours been “upside down” so the water can catch on the lip of the lid and seep in? Or was it right side up and is now only turned around because you replaced the relay?

 

Man that thing was just dangling there...held on by a zip tie...don't think there was any specific orientation.

 

Glad you got it fixed.
If you need wiring diagrams you can find them here..
They pop up as a PDF and can easily be enlarged on your screen.

Ultimate TUNDRA Wiring Diagrams Collection | Toyota Tundra Forum (tundras.com)

 

Bingo. Looks like when the relay box was put in during the recall, it was careless put in upside down so that water collected in the box.