ACDelco GM Original Equipment Anti-Theft Control Modules are one part of the vehicle’s theft deterrent system. When armed, the system is designed to deter vehicle theft by performing one or more of the following: pulsing the horns and exterior lamps when unauthorized vehicle entry is detected, or prevent starting of the engine without an authenticated ignition key. This module may manage the system functions independently or in conjunction with other modules and components within the vehicle. These original equipment anti-theft control modules have been manufactured to fit your GM vehicle, providing the same performance, durability, and service life you expect from General Motors.