Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
It means the Factory Security System is still Engaged & it has not been Disabled.Try :Shut ALL Doors, Trunk & Hood.Push Lock Button on Remote 2 Times ( Horn should Honk)Wait apprx 1 minute.Push Unlock Button on Remote.Open DoorPut Key Into Ignition & Start Vehicle.
If SECURITY still comes on, then you will have to have Chevrolet Service Scan Vehicle & Disable. It could be a problem with the Ignition Cylinder not recognizing Key Code