Engine Control Module/Powertrain Control Module (ECM/PCM)

IMPORTANT: On some vehicles, if the ECM/PCM is unable to communicate with the immobilizer system after the vehicle has started, the ECM/PCM will consider the immobilizer system to be malfunctioning. The ECM/PCM will enter a fail enable state. When the ECM/PCM is in a fail enable state the vehicle will NOT stall or stop running. If the ECM/PCM is in a fail enable state when the ignition is switched OFF, the ECM/PCM will remain fail enable until communications with the immobilizer system has been restored. When the ECM/PCM is in a fail enable state the immobilizer system is NOT active and the vehicle will start. This feature is NOT available on all GM vehicle lines.

The ECM/PCM verifies that the password received from the body control module (BCM) via the serial data circuit is correct. The PCM can learn only one fuel continue password. If the fuel continue password is correct, the PCM enables the starting and fuel delivery systems.

The ECM/PCM disables the starting and fuel delivery systems if any of the following conditions occur:

The fuel enable password is incorrect.
The fuel disable password is sent by the BCM.
No passwords are received-There is no communication with the BCM.