GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Each time the ignition cycles from OFF to ON, the radio receives VIN data over the class 2 communication circuit. If the VIN data in the radio memory matches the VIN data the radio receives over the class 2 communication circuit, the radio will operate normally.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B1780 Theftlock Enabled

Conditions for Running the DTC

    • The DTC is run when the radio is turned from OFF to ON.
    • Battery voltage is between 9-16 volts.

Conditions for Setting the DTC

Installing a radio from another vehicle or installing a new body control module (BCM) and not entering the correct VIN information with the scan tool.

Action Taken When the DTC Sets

The radio does not function. The radio displays "LOC" or "LOCKED" .

Conditions for Clearing the DTC

    • When installing a radio from another vehicle of the same platform, clear the VIN data using the scan tool.
    • Installing a new BCM setup properly with the correct VIN for that vehicle.

The DTC status will turn to history when the above criteria is met. The scan tool can now clear the history DTC, or the DTC will clear automatically after 100 consecutive fault free ignition cycles.

Test Description

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

  1. After clearing the DTCs and theft information, the radio relearns the VIN upon cycling the ignition switch.

  2. After completing the repair procedure, clear all DTCs.

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Use the scan tool to clear the DTCs.
  3. Perform radio setup procedure. Refer to Radio Setup .

Does the DTC Reset?

Go to Step 3

System OK

3

Replace the Radio. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

System OK

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