2000 Jeep Grand Cherokee • 137,000 miles

I ran the battery down over three days because I left the ignition on. Since then I have had intermittent immobilizer faults, it starts and dies like it should if I had a bad key. It does this with both keys.
I have disconnected the battery several times for a few minutes to over night. I turned it on with the key and had a charger on the battery over night it started and ran twice now back into fault.
I am about to scrap this thing I bought it 2 months ago it ran beautifully until killed the battery. The battery has been recharged and is only a year old and shows 12.7 on my VOM.
Am I experiencing a returning hard fault? Is that why sometimes it goes and more often not.
Thanks for your consideration.

January 28, 2013.

Bill: What is the fault code you are getting? It sounds like a problem with the security system. You will most likely need to have a dealer check the security because most likely they are the only ones that will have the right equipment to test it.