After a loss of battery power has been restored, the theft deterrent control module will perform a check on the stored vehicle identification number (VIN). If the VIN is CORRECT, the theft deterrent control module will run the VIN Timer for a programmable length of time, typically 10 minutes. The theft deterrent control module will send a message via the serial data circuit to the instrument panel cluster (IPC) to illuminate the SECURITY indicator. After the VIN Timer has timed out, the security indicator will turn OFF. If the VIN is INCORRECT, the theft deterrent control module will send the fuel disable password to the engine control module (ECM), via the serial data circuit. The vehicle theft deterrent (VTD) system considers this to be a tamper and will not allow the vehicle to start. The theft deterrent control module will send a message via the serial data circuit to the IPC to flash the SECURITY indicator.

Substitution detection is based on 4 correct responses from the following modules: IPC, rear integration module (RIM), driver door module (DDM), front passenger door module (FPDM), left rear door module (LRDM), and the right rear door module (RRDM). The modules compare their VIN to that stored in the VIN master on every ignition ON cycle and report their status to the theft deterrent module. The theft deterrent module will only check the modules status to see the 4 correct matches when a battery reconnect has been recognized within the theft deterrent module.

This diagnostic procedure supports the following DTC:

DTC B1015 Vehicle Identification Number (VIN) Information Error

The ignition is ON.

The VIN information is stored during the Setup New VTD Module procedure on a GM SPO replacement part. When the manufacturers enable counter (MEC) is equal to 0, the VIN information cannot be changed. DTC B1015 will set when both the theft deterrent module's stored VIN and the stored VIN of those modules which report to the theft deterrent module does not equal the VIN stored in the dash integration module (DIM). This situation may occur if the VIN was programmed incorrectly to the DIM. Other instances of DTC B1015 would be the theft deterrent module and any of the modules reporting their status to the theft deterrent module not being properly set up.

The numbers below refer to the step numbers on the diagnostic table:

2. This step checks the stored VIN of the VIN master. If the programmed VIN in the DIM is different than that of the actual vehicle VIN, DTC B1015 will be set.

4. This step checks the stored VIN of the 7 modules. If the theft deterrent module and any other of the 6 modules is mismatched to the VIN store in the DIM, DTC B1015 will set.