I should clarify, by security system, I am talking about the vehicle anti-theft system. Sometimes known by acronyms: SKIM, SKIS, SKREEM, they use their own module (a halo antenna around the ignition lock cylinder), and the PCM. The two have four digit PIN that needs to be programmed, and the two communicate this between each other, in order for the engine to run. While the security system involving door locks ties in with the BCM, and the SKIM (it uses the proper key in the ignition as another means to disable the alarm), it is not the same. The PCM has been incorporated in the anti-theft system since the mid-90's to present (though the modern systems have changed slightly, along with their acronyms, such as WIN, and KIN).
