Powertrain Control Module
WARNING: This page is about a different car, the 2001 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
Powertrain Control Module (PCM) communicates with Instrument Panel Cluster (IPC) over class 2 serial data line. When IPC enters tamper mode, it sends a class 2 serial data signal to PCM in order to disable fuel injection system. If IPC receives expected ignition code, IPC sends a class 2 serial data signal to PCM in order to enable fuel injection system. PCM then allows vehicle to start.