Engine Control Module (ECM) & Theft Deterrent Control Module

ENGINE CONTROL MODULE (ECM)

The ECM verifies that the password received from the theft deterrent control module via the serial data circuit is correct. The ECM can learn only one fuel continue password. If the fuel continue password is correct, the ECM enables the starting and fuel delivery systems.

The ECM disables the starting and fuel delivery systems if any of the following conditions occur:
- The fuel continue password is incorrect.
- The fuel disable password is sent by the theft deterrent control module.
- No passwords are received - there is no communication with the theft deterrent control module.

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