2005 GMC Safari Owner's Manual - Page 161

Activating the Theft-Deterrent Feature The instructions which follow explain how to enter your secret code to activate the THEFTLOCK® system. Read through all nine steps before starting the procedure. If you allow more than 15 seconds to elapse between any steps, the radio automatically reverts to time and you must start the procedure over at Step 4. 1. Write down any three or four-digit number from 000 to 1999 and keep it in a safe place separate from the vehicle. 2. Turn the ignition on. 3. Turn the radio off. 4. Press the 1 and 4 pushbuttons at the same time. Hold them down until --- appears on the display. Next you will use the secret code number which you have written down. 5. Press MN and 000 will appear on the display. 6. Press MN again to make the last two digits agree with your code. 7. Press HR to make the first one or two digits agree with your code. 8. Press AM FM after you have confirmed that the code matches the secret code you have written down. REP will appear on the display to indicate that Steps 5 through 7 need to be repeated to confirm your secret code. 9. Press AM FM again. SEC will appear on the display to indicate that the radio is secure. The LED indicator by the volume knob will begin flashing when the ignition is turned off. 3-51