2002 GMC Envoy XL Antitheft System Control Module Replacement Cost

Anti Theft and theft deterrent systems have become more advanced over the recent decades. They have moved from Anti Theft devices bought from a store all the way to transponders in ignition keys or smart keys that must be present and accurate in order for the vehicle to start and run. This leap in technology has changed the required systems to computer based systems which require a dedicated computer (or control module) in order to facilitate the security of the vehicle. The anti theft system control module goes by many names according to the year, make, and model, but they all perform the same function - keeping your vehicle in your hands.

Earlier systems used only a resistor in the ignition key. This resistor would intercept voltage from the anti theft control module, and return a modified voltage, signaling that it was the proper key. Now, transponders are used, and the Anti Theft module can actually read information from the key like an RFID tag. This information has to match the information in the anti theft control module exactly, and in some cases, the body control module will play a role in validating this information before sending the signal to the powertrain control module to start the engine. In all cases, the basic function of the anti theft control module is to disable the vehicle or sound the alarm when an improper key is used to access the vehicle or attempt to start the engine.

Everyone has heard a car honking wildly in a parking lot with all of the exterior lights flashing, and many people have tried to unlock their door or start their engine to find that their car has become that car. Besides the obnoxious honking and flashing lights, clicking relays will be heard inside the cabin of the vehicle, plus some sort of security light will illuminate of blink, and a message may appear on the instrument cluster to inform you of the security issue. Vehicles equipped with satellite connected alarms will be placed in contact with a representative from the service provider, and the engine may crank but not start, or do nothing. Luckily, the radio should function just fine, as well as other accessory systems.