The Door Open message might indicate that your door optics are bad.
I would however not even look at that until you get rid of the battery low message.
You either have a bad battery, perhaps its not making proper contact, shorted, installed incorrectly, etc.
Have you measured it with a meter and if so what voltage is it reading ?
Can you post a picture of your board. Often cell phone pictures are too big so if you email it to yourself you get the option to make the picture smaller in size.