Taillights, wiring harness and grounding oh my!

Hey guys I need some help troubleshooting. My passenger side taillight/brake light and passenger side license plate light are not working. My turn signals and backup lights work fine.
So far I have tried replacing the taillight (LED), wiring harness and grounding, as well as checking any fuse that could be related to the problem. None of these have worked so far and I’m at a loss of what to try next. Thanks for your help!

 

I'm by no means an expert but I would check for power with a multimeter. There's a thread up in here somewhere that scared me off from going LED ... something to do with CANBUS.

 

So it is the brake/stop, parking light, and plate light on the right/passenger side?

Doubt it's a fuse, both sides are the same circuit.

Brake light




Parking and plate light.



The only thing these 3 issues have is a common ground.
But the turn signal and backup light use the same ground pin 6 of the R4 connector.





But then I noticed this..



Are you using aftermarket tail lights or LED bulbs in OEM housings?
I'm guessing aftermarket tail lights but not sure why the plate light isn't working, or is it an LED bulb as well?

Did they ever work properly, or did they work and no longer work?

 

Thank you for the detailed response!

Yes, it’s the passenger brake light, running light, and plate light.

I bought the truck and all of the lights were already upgraded to LEDs. Both sides of the license plate lights flickered slightly when I bought it but the passenger side has since gone out completely. The LED tail lights, which come in their own housing unit, both worked fine until the passenger went out.

 

As @Tunrod suggested, I'd check the sockets/plugs with a DDM (digital multi meter).
Check for power and proper ground.

I'd replace both plate lights and see if that fixes the plate light issue.
Those lights don't depend on the tail light working or not.

You said you replaced the aftermarket tail light as well?
It might have a bad circuit board in it..