Vehicle Theft Detection (VTD)

POWERTRAIN CONTROL MODULE (PCM)

The PCM verifies that the password received from the theft deterrent control module via the Class 2 serial data circuit is correct. The PCM can learn only one enable password. If the enable password is correct, the PCM enables the starting and fuel delivery Systems. The PCM disables the starting and fuel delivery systems if any of the following conditions occur:
- The enable password is incorrect.
- The system 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 PCM is unable to communicate with the VTD system after the vehicle has started, the PCM will consider the VTD system to be malfunctioning. The PCM will enter a fail enable state and will command the security indicator to illuminate. When the PCM is in a fail enable state the vehicle will NOT stall or stop running. If the PCM is in a fail enable state when the ignition is switched OFF, the PCM will remain fail enable until communications with the VTD system has been restored. When the PCM 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.