2000malibu

What do you mean? The car will not start and the security light is flashing when you try to start it? Have you recently replaced a key? Is there more than one key for the vehicle? Sometimes only 1 key of the 2 that came with it will allow the engine to start and the other key is only for unlocking the locks on the vehicle. If you recently replaced the key, the new one will only work if it is programmed to the vehicle and any other keys will lose functionality unless they were programmed along with the new key.

I have a 2001 and the guy at the dealership said these cars don't have transponder or chip keys. These cars didn't get those until some time later than 2001. I had to replace the passkey censor in the ignition. That got rid of the security light, but it still just cranks without starting.