HouseCallAuto 5/14/2013Try to start the car with a different key. there is a transponder in the key. Sometimes the transponder goes bad and the key cannot establish a link with the vehicle security module so the computer thinks the vehicle is being tampered with so the anti-theft kicks in and does not allow the engine to start. If this is the case, there would also be a light illuminated on the dash that might say anti-theft or security while trying to start the engine. If the spare key does not work then the car will need to go to a shop to diagnose and repair. You cannot diagnose anti-theft causes without the use of a professional scan tool that gives live data.