Radio 'LOCKED'

I just bought a 2002 Grand AM, and the radio displays 'LOCKED'.
I tried:
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Looking at the face of your GM Delco radio, hold down the preset buttons 1 & 4 OR 2 & 3 (Depending on year and model) for approximately 10 seconds or until a set of 2 or 3 numbers comes up on the display. Write the numbers down.

But the radio continues to display 'LOCKED', and no numbers appear.
Any suggestions?

Your 2002 uses Class 2 serial data. Does not have the same unlock proceedure as the older models. The only way to unlock your radio is with a Tech 2 scanner.

Thank You.