Hello and thank you for using justanswer, my name is ***** ***** I will help you with your problem.
You need to do a passlock reset if the security light is flashing and car wont start. This should get the car running again. There are two different ways to perform the reset procedure, one is by using a dealer scan tool, the other is a 30 minute diy procedure. I'm assuming you don't have access to the dealer scan tool so here is the 30 minute procedure.
30-Minute Learn Procedure
Be sure the Battery is fully charged and can withstand 30 minutes of draw.
Connect Battery Charger if you are not sure.
Important: Do not remove the key from the ignition during this procedure. If the key is removed, the procedure will have to be performed from the beginning.
1) Turn ON the ignition, with the engine OFF.
2) Attempt to start the engine, then release the key to ON. The vehicle will not start.
3) Observe the SECURITY telltale. After approximately 10 minutes , the telltale will turn OFF.
4) Turn OFF the ignition, and wait 5 seconds .
5) Repeat steps 1-4 two more times for a total of 3 cycles/30 minutes . The vehicle is now ready to relearn the Passlock Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK.
6) Important: The vehicle learns the Passlock Sensor Data Code and/or password ***** next ignition switch transition from OFF to CRANK.
You must turn the ignition OFF before attempting to start the vehicle.
Start the engine. The vehicle has now learned the Passlock Sensor Data Code and/or password.