Taillights malfunction, the left taillight is out for signaling?

The first thing we need to do is check all fuses with the system on this guide can help and I have left the fuse location in the images below.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

If the fuses are okay, you need to remove the rear light bulbs in question to see if any filaments or bulb contacts have melted together. Please check out this guide to see what I am talking about:

https://www.2carpros.com/articles/no-tail-lights-exterior-running-lights-tail-lights-out

Next, we need to check the grounds to the system because it could be the "vehicle electrical system control module" or the "comfort system central control module". Which would require a CAN scan to see which module is out. You can get a CAN scanner (Controller Area Network) from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Here is one for about $99.00 if you need it:
https://amzn.to/3ZixY4v

Here are the running light wiring diagrams so you can see how the system works and which fuses to check. Check out the images (below). Let us know what happens and please upload pictures or videos of the problem so we can see what's going on.

Please tell your son thank you for his service. I am glad we helped. Thanks for letting us know, we are here to help, please use 2CarPros anytime.