Ok if the security light is flashing Here is how to re set it
Follow the steps 1 by 1
put in the key turn to on, ( do not try to start) For 10 minuets After 10 minuets turn off the key
Do not remove the key
leave off 10 minuets
turn on 10 minuets ( again do not try to start) after 10 minuets turn off but do not remove key
Leave off another 10 then turn on again for 10 again do not try to start.
After you have don this 3 times on and 3 times off, turn on for the 4th time wait 10 minuets then try to start. If the security light comes on and stays on, car will now start.
If it is still flashing, you will have to have the cylinder lock replaces with a new chip.