Parasitic drain

Well, I have been testing my friends Jeep and just occasionally tinkering and found that when I unplugged the BCM, the spark when putting the terminal on the post, was not even noticeable.
I did get them to get a new battery, and I started the jeep and it runs smoothly and no warning lights in the dash come on. Just the one rear passenger door indicator still says it is open.
It would not throw any codes either since there was no power for so long. I did remove the door latch and only found that you must replace it as there is no way to repair it. But strangely, the red indicator light I think is for alarm system, is on top of the dash, not in it, it stays on solid instead of flashing. I fixed their Honda's heater core so it has not been a priority for the Jeep but it does seem as though I have found the main issue for drain yet the solid red light does seem suspect.