Getting a check engine light after changing battery

If that's the case flash the computer-

Got'cha! GM has designed in a lot of things to separate you from your money after the sale. Everyone knows you can't disconnect the battery or allow it to run dead. They make units with little transistor radio batteries called "memory savers" to keep the many computer memories intact while replacing the battery. The fix now is to tow it to the dealer and spend lots of money to have them unlock the computers or reinstall the software. Not all of the computers will need to have that done, but there can be up to 47 computers doing things we never needed computers for before. The engineers are insane. That's true of all of the manufacturers, but GM is by far the worst at preventing independent shops from working on their products. It's how they stay profitable but it's also why they can't find any repeat customers to buy their cars.