Expert: Mike Evans - 7/20/2010

Question
Mike: Can I change my 2005 Sonata battery with one from Costco (Signature Series)? I have been cautioned that to do this myself, I will lose the "electronic data" in storage unless I have the proper storage/capture devise that will hold data and then return it to the auto after it is installed. Your thoughts please. Many thanks. Marty

Answer
    You will not lose data from the ECM, it is designed to retain everything during a battery change.  You will lose radio presets, and will have to reset the radio security code (if it uses one).  If you want to be very thorough you can buy or borrow a little gizmo (any auto parts store should have them) that uses a 9V battery jacked into the cigarette lighter socket to make sure minimal voltage continues to be supplied to the circuits.  Any data lost from the ECM will just be the record of your last 30 minutes of driving, which would be overwritten next time you drive it.

    Speaking of which, if you are ever in an accident where there is some question of your having been driving correctly, you should leave the ignition on with the motor running for as long as possible so that the ECM will write over any incriminating data.  Otherwise the police accident investigators can retrieve the data and use it against you (also the insurance investigators).  Obviously this would not apply in the case of a fire or any conditions that might result in fire (fuel leak, etc.).