disarm anti theft security?

Cant, the security system is integrated into the BCM so it must be disarmed to have the engine start. To reset the system please follow this link.

https://www.2carpros.com/articles/how-to-reset-a-security-system

When you try to start the truck does the security light flash? If so this is the problem. Do you have the fob still? Please go over the guide to let me know what happens.