GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B1780: Theft Lock Enabled

Circuit/System Description

To deter theft, the radio learns and stores the vehicle VIN. If the radio is removed from the vehicle and installed into another vehicle, the radio performs a VIN check. If the VIN stored in the radio and the VIN being reported over serial data do not match or no VIN is received, the radio will go into a theft lock state and be inoperative.

Conditions for Running the DTC

This test is run every 300 milliseconds.

Conditions for Setting the DTC

    • The VIN received over serial data and the VIN as stored in the radio memory do not match.
    • No VIN is received over serial data.

Action Taken When the DTC Sets

Radio functions are suspended. The radio will display LOC, LOCK, or LOCKED.

Conditions for Clearing the DTC

The DTC will clear when a valid VIN is received.

Reference Information

Schematic Reference

Radio/Navigation System Schematics

Connector End View Reference

Entertainment/Communication Connector End Views

Description and Operation

Radio/Audio System Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Circuit/System Verification

Ignition ON, perform theft radio setup procedure. Refer to Radio Programming and Setup. Verify the DTC does not reset.

If the DTC resets, replace the radio.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for radio replacement, programming, and setup