Left rear taillight assembly not working

We need to check the voltage that is getting to the rear taillight assembly to see if there is anything there.

Here is a guide that will help with this:

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-use-a-voltmeter

I am attaching the wiring diagram below as well that will help with this. However, you have a single wire coming in that we need to check when you have the lights turned on.

It is unlikely that this is a ground issue since it appears they are shared ground for the rear lights so let's start with checking what is there, and I am sure we will find a wiring issue or a fuse block issue.

Let me know what questions you have.

Thanks