1. Turn the ignition key to the "On" position and leave it there for 10 minutes.
2. The security indicator light should begin flashing after 10 minutes.
3. Press and hold the "Unlock" button on the driver's door for 5 seconds.
4. The security indicator light should turn off.
5. Turn the ignition key to the "Off" position.
6. Wait 1 minute and then try to start the vehicle.
The security system should now be reset. If the problem persists, you may need to take your vehicle to a qualified mechanic for further diagnosis and repair.