The security light blinking indicates it has failed the security password. That is usually caused by a bad ignition lock but sometimes is just a fluke.
I'm giving you the relearn procedure for that. This may or may not work. If it does not, then you have a hard failure and you will need a Tech2 scan tool to be able to diagnose the problem.
Make sure you have a fully charged battery before attempting this.
30 Minute Re-Learn Procedure
1. Turn ON the ignition, with the engine OFF.
2. Attempt to start the engine, then release the key to ON (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 through 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).
The vehicle learns the Passlock√ Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.
6. Start the engine (the vehicle has now learned the Passlock√ Sensor Data Code and/or password).
7. With a scan tool, clear any DTCs if desired (history DTCs will self clear after 100 ignition cycles).
Saturday, August 28th, 2010 AT 7:06 PM