How do I reset theft system on 2000 chevy malibu?

Resetting and normal disabling look the same with Your 2000 Chevrolet Malibu. If Your vehicle's horn is currently sounding and the headlights are flashing on and off, You're going to want to deactivate the alarm. Do this by pressing the "Unlock" button, which typically has a symbol of an open lock. You can also unlock the doors of Your car with the proper key and turn the ignition on. These are the only two ways You can deactivate the alarm, though, if You've got a door already open, You could pop the hood and disconnect the battery if You for some reason can't use the keys and must turn off the horns/lights. After You've deactivated it (with the keys!), press the lock switch from inside the car to lock the doors; make sure everything is properly closed. Wait for the security light to stop flashing from inside the car. When it stops flashing, You can then press the unlock button and exit the vehicle.