Powertrain Control Module
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.
The powertrain control module (PCM) contains the remainder of the logic of the Theft Deterrent System. If a class 2 message containing a valid password is received from the body control module (BCM), the PCM will continue to allow the fuel injectors to operate. The PCM will allow the fuel injectors to operate until it decides there is no valid password coming from the BCM. If the PCM does not receive a class 2 message, or receives a class 2 message with an incorrect password, the engine will crank and will not run or will start and stall immediately.