GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Theft protection ON mode is active when a valid VIN has been stored in the radio and the last reported VIN matches. Any time the VIN is reported it is compared to the stored VIN.

Theftlock mode is active when a valid VIN has been stored in the radio and the last reported VIN does not match. Theftlock mode is also active when a valid VIN has been stored in the radio and no VIN has been reported since the battery has been disconnected and then reconnected.

Conditions for Setting the DTC

    • DTC B1780 will set if the last reported VIN does not match the stored VIN.
    • DTC B1780 will also set if no DTC has been reported since the battery has been disconnected and then connected.

Action Taken When the DTC Sets

    • DTC B1780 will be stored in the IRC memory.
    • The radio will display "LOC" when it is turned ON.
    • The radio will not play anything even though it is turned ON because the Theftlock is activated.

Conditions for Clearing the DTC

DTC B1780 will automatically clear when the IRC receives the correct production sequence number (the last six digits of the VIN) from the scan tool over the class 2 data line.

Diagnostic Aids

  1. Turn the ignition switch to the ON position.
  2. Use the scan tool to clear DTC B1780.
  3. Cycle the ignition.
  4. Replace the radio if DTC B1780 is still present. Refer to Radio Replacement in Entertainment.