What is remote start bypass module?

Most modern vehicles have some type of passive anti-theft system. The systems vary from vehicle manufacturer to manufacturer but most work in the same way. GM used to use resistance based anti-theft systems activated by either a resistor in the blade of a key (VATS), or a resistor in the ignition switch (passlock or passlock II). Most other manufacturers use a transponder based system. A transponder is essentially a small chip in the plastic head of the key that the vehicle has to see in order to start. A bypass module simulates whatever the vehicle needs to see, but only when remote starting. This allows the factory system to remain completely intact and still allows you to add a remote starting system to the vehicle.