2002 Chevrolet Silverado 1500 Pickup Owner's Manual - Page 226

If you enter the wrong code eight times, INOP will appear on the display. You will have to wait an hour with the ignition on before you can try again. When you try again, you will only have three chances to enter the correct code before INOP appears. If you lose or forget your code, contact your dealer. Disabling the Theft-Deterrent Feature Enter your secret code as follows; pause no more than 15 seconds between steps: 1. Turn the ignition to ACCESSORY or RUN. 2. Turn the radio off. 3. Press the 1 and 4 pushbuttons at the same time. Hold them down until SEC shows on the display. 4. Press MN and 000 will appear on the display. 5. Press MN again to make the last two digits agree with your code. 6. Press HR to make the first one or two digits agree with your code. 7. Press AM FM after you have confirmed that the code matches the secret code you have written down. The display will show ---, indicating that the radio is no longer secured. If the code entered is incorrect, SEC will appear on the display. The radio will remain secured until the correct code is entered. When battery power is removed and later applied to a secured radio, the radio won't turn on and LOC will appear on the display. To unlock a secured radio, see "Unlocking the Theft-Deterrent Feature After a Power Loss" earlier in this section. 3-24