You need to have the computer coded out. A plain code reader will not recover antitheft codes. Look on craigslist in automotive services to see if someone will come out to scan the car with a scanner that can scan security codes. Once you have the codes post them on RepairPal for us to help you.
Take the keys out of the vehicle ,lock the vehicle & then unlock the drivers door with the key.This will tell the computer that you are the owner.
If the security light is flashing you may need to do a relearn procedure.
Turn ON the ignition, with the engine OFF. Attempt to start the engine, then release the key to ON (vehicle will not start). Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF. Turn OFF the ignition, and wait 5 seconds. Repeat steps 1 through 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the password XXXXX the next ignition switch transition from OFF to CRANK).
Important: The vehicle learns the password XXXXX the next ignition switch transition from OFF to CRANK. You must turn the ignition OFF before attempting to start the vehicle.