Powertrain Control Module
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2004 GMC Yukon XL, 2004 GMC Yukon, 2004 Chevrolet Tahoe, 2004 Chevrolet Suburban, and 2004 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
The powertrain control module (PCM) determines the driver's intent, then calculates the appropriate throttle response. This information is sent to the throttle actuator control (TAC) module through a dedicated serial data line.