Module, Vehicle Tracking (VTM): Operation

In normal operation, each time the ignition switch status transitions from Off to On the Body Control Module (BCM) will request a code status request from the Vehicle Tracking Module (VTM) (also known as the Vehicle Theft Module/VTM) using electronic messaging over the Controller Area Network (CAN) B network. Upon receiving the BCM request the VTM will send the code status reply to the BCM, also using electronic messaging over the CAN B network.

If the vehicle is stolen the owner can contact the Service Provider (SP) and request that the vehicle code status be revised to Blocked  . The SP sends a code status update command to the VTM, and the VTM stores the Blocked  code status in memory. The next time the ignition switch status transitions from Off to On and the BCM requests the code status from the VTM, the VTM will respond with a Blocked  status message back to BCM and the engine will not start. In addition to preventing the vehicle from starting, the VTM will also generate a message back to the SP containing the Global Positioning System (GPS) coordinates indicating the current position of the vehicle. If the vehicle battery is disconnected or discharged, the VTM has an internal back up battery to power the module for several hours.

Once the vehicle has been recovered, the owner contacts the SP and requests that the vehicle code status be restored to Unblocked  . The SP sends a code status update command to the VTM, and the VTM stores the Unblocked  code status in memory. The next time the ignition switch status transitions from Off to On and the BCM requests the code status from the VTM, the VTM will respond with an Unblocked  status message back to BCM and the engine will be allowed to start.