That is correct. the older radios would show loc, and a simple unlock procedure with a code would unlock the radio. the newer radios have to be set-up and programmed with a GM tech 2 scan tool. but after reviewing your question a little more. if the display is blank, this can only be a bad radio. which is real common on these vehicles. but after installing a know good radio, it has to be programmed with the vin number so it will operate correctly.
Perform the radio set up procedure
To setup a new radio for the vehicle, complete the setup procedure under the Special Functions menu of the scan tool.
If the new radio is not properly setup, the radio will display a locked message (LOC) or Calibrate.
Important: The radio set up will configure the following systems:
|• ||Steering Wheel Controls|
|• ||Diagnostic Trouble Codes|
Without learning the VIN, the radio will display a locked message (LOC).
The "Theftlock" theft deterrent system is a feature on all base and uplevel radios. There is no need to program a security code into the radio as in past model years. The theft deterrent system now utilizes class 2 serial data to determine if the radio is in the appropriate vehicle. Each time the radio receives the "run" power mode message, it compares the VIN information it has stored to the VIN information received from a module on the class 2 serial data circuit responsible for transmitting that information. If a mis-match occurs, the radio display will indicate to the user the radio is locked. Once this takes place, a DTC will set, the radio will not respond to any button presses and become inoperative. The two scenarios able to cause this condition are:
|• ||A radio is installed from another vehicle.|
|• ||A module which communicates on the class 2 serial data circuit which supplies VIN information to the radio is replaced and not properly setup with the correct VIN information for that vehicle.|
The only way to unlock the radio is by using a scan tool. Always refer to the table in this section to diagnose the "Theftlock" DTC for further information.