Q: Security light flashes rapidly trying to start truck everything comes on but it won't start

You may still be in lockout and the security system is keeping you from starting the car. When the car was entered without the key, it no doubt triggered the immobilizer and that will have to be reset. It’s might be just as simple as re-booting your computer. Try closing and locking all the doors, activating the security system as you do so. Then unlock the door with the key and get in the truck and try to start it as you normally would. That might be all that it takes. If that doesn’t work, the next step is to read the system with a scanner. Contact Your Mechanic to have a technician come out to your home or office to check out your Pickup and let you know what it is going to take to fix it.