GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Astro - 4WD 🢒 Body and Accessories 🢒 Entertainment 🢒 Radio/Audio System Operation-Theftlock

Theft Deterrent (THEFTLOCK)
    • The radios are equipped with THEFTLOCK theft deterrent.
        The THEFTLOCK theft deterrent causes the unit to be inoperative should the radio be removed from the vehicle.
    • The theft deterrent is enabled (SECURE mode) by entering a user-selected code into the unit.
    •  The user-selected code must be re-keyed into the unit following any interruption of battery voltage to resume normal operations.
    • This code must be re-keyed into the unit following any interruption of battery voltage to resume normal operations.
    • If the correct code is not entered, the unit will become inoperable and remain in the LOCKED mode.
    • Any theft deterrent input mode may be exited by cycling either the radio power or ignition.

Activating Theftlock

In order to activate the THEFTLOCK theft deterrent, perform the following steps:

  1. Write down any number from 000 to 1999. Keep this number in a secure place.
  2. Turn the ignition to the ACC or the RUN position.
  3. Turn the radio OFF.
  4. Press the 1 and the 4 push-buttons together. Hold them down until -- shows on the display.
  5. You are now ready to enter your code. Do not wait more than 15 seconds between each step.
  6. Press MIN 000.

    7. MIN 000 will appear on the display.

  7. Press the MIN push button again in order to make the last 2 digits agree with your code.
  8. Press the HR push button in order to make the first 1 or 2 digits agree with your code.
  9. Press the AM/FM push button after you have confirmed that the code matches the code you wrote down. REP appears on the display, indicating that steps 5-7 need to be repeated.
  10. Press AM/FM. This time the display will show SEC. SEC means that your radio is secure.

    11. Important: With the ignition OFF, the THEFTLOCK indicator will flash.

To Unlock THEFTLOCK After a Power Loss

In order to unlock the THEFTLOCK system after a power loss, enter the user code as follows (do not wait more than 15 seconds between steps):

    • Press MIN.
         000 will appear on the display.
    • Press the MIN push button again in order to make the last two digits agree with your code.
    • Press the HR push button in order to make the first one or two digits agree with your code.
    • Press the AM/FM push button after you have confirmed that the code matches the one you wrote down.
        SEC will appear in the display indicating that the radio is now operable.