I have a 2002 malibu and the theft system light is on. Also the temp gauge and gas guage go on and off. The speedometer and tack go wacky occasionally. The brake light and airbag light come on sometimes and something is causing the battery to go dead. The battery is brand new and the altenator is good.
Really sounds like a bad body control module you would have to do a lot of testing to see that is was a bad body control module. Do you have a multimeter know how to test for power grounds etc?Also read wire diagrams?