2020 Halogen Tundra Odd Headlight Issue

Hey all, new here. Lurked for a while and finally decided to create an account after not being able to find good resources of others with a similar experience.

2020 Tundra SR5 owner, absolutely love the truck and she’s been super reliable since day one. Quite a few months back there started to be an issue with the driver head light where it would be on normally on my AM drive to work and then it would seemingly randomly phase in and out of operating. Not like a quick repeated occurrence, more like it would be on a few minutes, turn off a few others with no consistent pattern. At that point I could flip to high beams and still get both headlights working consistently 100% of the time.

Fast forward a period of time after that and that headlight low beam straight up stopped working. I stopped using my low beams at that point and would just run the LED DRLs as I wasn’t really doing much driving at night. Eventually the high beam on that side stopped working entirely and the high beam on the passenger started giving issues as well.

I recently decided to grab new headlights as that is the obvious and easy fix to do. Ended up swapping them, that didn’t change anything so today I was able to set aside time and take a deeper look; leading up to this I ordered some H7 light bulb socket connectors as I had noticed when changing the headlights prior that the cavities that lead to exposed conductor on the oem connector were seriously gummed up and I thought that might be causing a short.

long story short I ended up taking a bunch of electrical measurements and noticed that there’s a much more dubious cause here.

At the low headlight right & left 15A fuse in the engine fuse box, I’m getting -13.7v to ground both sides. High beams, whether engaged or not, do not have voltage going through them at the High headlight fuse location, left or right. I swapped the dimmer relay with an identical relay from the fog lights to rule that out; swapping that relay didn’t change anything. I then swapped the H-LP Lo relay with the battery charger relay to see if I could get the right power to the driver side headlight and that didn’t work either.

where it gets weird is this: from the three headlight wires on the driver side, I’m getting -4v from hi to G, -7 from Low to G, & -11v from Hi to Low. The other headlight shows a normal -13v from low to ground, and nothing from high to ground.

my instinct here tells me there is a short somewhere between the fuses and the headlight connector if I’m getting 13 volts from the associated low fuses to ground so up to that point it seems good. I’m unsure what would be causing the high side fuses not to energize when the high beams are engaged.

Wondering if anyone has any advice here.