GM Service Manual Online
For 1990-2009 cars only

The following instructions explain how to enter a secret code to activate the THEFTLOCK™ system.

Read all nine steps before starting the procedure.

Important: If more than 15 SECONDS is allowed to elapse between any steps, the radio automatically reverts to displaying time and the procedure must be started over at Step 4.

  1. Write down any three or four-digit number from 000 to 1999. Keep the number in a safe place separate from the vehicle. This number is the secret code.
  2. Turn the ignition to the ACCESSORY or RUN position.
  3. Turn the radio OFF.
  4. Press the number 1 and 4 push buttons at the same time. Hold the number 1 and 4 push buttons down until "- - -" appears on the VF display.
  5. Press MN.
  6. 000 will appear on the display.

  7. Press MN again until the last two digits agree with the last two digits of the secret code.
  8. Press HR until the first one or two digits agree with the first one or two digits of the secret code.
  9. Press AM/FM after confirming that the display code matches the secret code. REP appears on the display indicating that Steps 5 through Step 7 need to be repeated to confirm the secret code.
  10. Press AM/FM again. SEC appears on the display indicating that the radio is secure. The indicator light by the PWR-VOL control begins flashing when the ignition is turned off.