Our car is doing the same thing. Also can pull shifter out of park while car is off and key removed. This leaves power on and drains the battery down. I replaced the electrical part of the ignition switch and it did nothing to solve this issue. I have ordered and received yesterday but have not installed as of yet the new tumbler and keys. I have the instructions from a GM Master Mechanic the proceedure on how to relearn the car to your new keys if you decide to do the same thing. A new tumbler and key set is like $24.50 tax and shipping from Rockauto. I plan to install this week and will report back the results on my Continuous battery draining thread I started a week or so back. Be happy to give you the results on here as well. If you decide to change tumbler and keys let me know if you need the instructions on how to relearn the keys to the computer and I will PM them to you.
