Left rear door ajar light and interior lights are on draining the battery?

Yes, if one of the doors remains open it can drain the battery down. What happens is the micro switch inside the latch goes bad and makes the BCM think the door is still open. Also, you may have a bad battery, can I ask how old it is? This guide can help us load test the battery or you can remove it and take it to the auto parts store:

https://www.2carpros.com/articles/car-battery-load-test

Here is how to change out the door latch to help stop the drain. Also, I have included a generic guide on how to swap out the battery.

https://www.2carpros.com/articles/how-to-replace-a-car-battery

Check out the images (below). Let us know how it goes.

I don't know if pulling the fuse will help because if the BCM sees the door open it will not allow the system to "sleep" and drain the battery down. If you have a CAN scanner it might have a code that can confirm or lead us in the right direction. You can get a CAN scanner (Controller Area Network) which will work on most cars 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

This guide may help as well:

https://www.2carpros.com/articles/car-battery-dead-overnight

Please go over these guides and get back to us.