GM Service Manual Online
For 1990-2009 cars only

The radio has the theft deterrent feature if THEFTLOCK appears on the face of the radio. THEFTLOCK™ is designed in order to discourage theft of the radio. THEFTLOCK™ works by using a secret code in order to disable all of the radio functions whenever the battery power is removed.

If THEFTLOCK™ is active, the THEFTLOCK™ indicator flashes when the ignition is OFF.

The THEFTLOCK™ feature for the radio may be used or ignored. If the THEFTLOCK™ feature is ignored, the following conditions exist:

    • The system plays normally.
    • The radio is not protected by the THEFTLOCK™ feature.

If THEFTLOCK™ is activated, the radio will not operate if stolen.

When THEFTLOCK™ is activated, the radio will display LOC in order to indicate a locked condition anytime the battery power is removed. If the battery loses power for any reason, you must unlock the radio with the secret code before the radio will operate.

Activating the Theft Deterrent Feature

The following instructions explain how to enter a secret code in order to activate the THEFTLOCK™ system. Read through all 9 steps before starting the procedure.

Important: If you allow more than 15 seconds to elapse between any of the steps, the radio display will automatically revert to time and you must start the procedure over at Step 4.

  1. Write down any 3 or 4 digit number from 000-1999. Keep the number in a safe place separate from the vehicle.
  2. Turn the ignition to one of the following positions:
  3. • ACC
    • RUN
  4. Turn the radio OFF.
  5. Complete the following steps:
  6. 4.1. Press the 1 and 4 buttons together.
    4.2. Hold the buttons down until - - - shows on the display.
    4.3. Refer to the secret code number that you wrote down.
  7. Press MN. 000 will appear on the display.
  8. Press MN again in order to make the last 2 digits agree with the code.
  9. Press HR in order to make the first 1 or 2 digits agree with the code.
  10. Press AM/FM after you have confirmed that the code matches the secret code that was written down. The display will show REP in order to let you know that you need to repeat steps 5-7 in order to confirm the secret code.
  11. Press AM/FM. This time the display will show SEC in order to let you know that the radio is secure. The indicator by the volume control will begin flashing when the ignition is turned OFF.

Unlocking the Theft Deterrent Feature After a Power Loss

Complete the following steps in order to enter the secret code, pausing no more than 15 seconds between steps:

  1. LOC appears when the ignition is ON.
  2. Press MN. 000 will appear on the display.
  3. Press MN again in order to make the last 2 digits agree with the code.
  4. Press HR in order to make the first 1 or 2 digits agree with the code.
  5. Press AM/FM after you have confirmed that the code matches the secret code that was written down. The display will show SEC, which indicates the following conditions:
  6. • The radio is now operable.
    • The radio is secure.

If the wrong code is entered 8 times, INOP will appear on the display. You will have to wait 1 hour with the ignition ON before you can try again. When you try again, you will only have 3 chances to enter the correct code before INOP appears.

Disabling the Theft Deterrent Feature

Enter the secret code as follows, pausing no more than 15 seconds between steps:

  1. Turn the ignition to one of the following positions:
  2. • ACC
    • RUN
  3. Turn the radio OFF.
  4. Perform the following steps:
  5. 3.1. Press the 1 and 4 buttons together.
    3.2. Hold the buttons down until SEC shows on the display.
  6. Press MN . 000 will appear on the display.
  7. Press MN again in order to make the last 2 digits agree with the code.
  8. Press HR in order to make the first 1 or 2 digits agree with the code.
  9. Press AM/FM after you have confirmed that the code matches the secret code that was 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 given to a secured radio, the following conditions occur:

    • The radio does not turn ON.
    • LOC will appear on the display.

Removing Customer's Code

Important: You can use either of the following codes in order to remove the customer code:

   • The code chosen by the customer
   • The factory backup code

  1. Turn the ignition to one of the following positions:
  2. • ACC
    • RUN
  3. Turn the radio OFF.
  4. Important: If the display changes to - - -, the theft deterrent is already deactivated. No code is stored.

  5. Press the 1 and 4 pushbuttons together for about 6 seconds until the display changes to SEC.
  6. Press the HR button.
  7. Set the first 2 digits (0-19) of the code with the HR button.
  8. Set the next 2 digits (0-99) of the code with the MN button.
  9. Press the AM/FM button in order to enter the code. This action deactivates the theft deterrent.
  10. The following items will display:

    7.1. - - -
    7.2. The clock

Adding Customer's Code

  1. Turn the ignition to one of the following positions:
  2. • ACC
    • RUN
  3. Turn the radio OFF.
  4. Important: If SEC is displayed, the theft deterrent is already activated. Remove the old code before you enter a new code.

  5. Press the 1 and 4 pushbuttons together for about 6 seconds until the display changes to - - -.
  6. Press the HR button.
  7. Set the first 2 digits (0-19) of the code with the HR button.
  8. Set the next 2 digits (0-99) of the code with the MN button.
  9. Important: If - - - is displayed after pressing AM/FM, the customer code has not been entered.

  10. Press the AM/FM button in order to enter the code.
  11. When REP then 000 are displayed, repeat steps 3-5. Repeating these steps achieves the following results:
  12. • Confirms the customer code.
    • Activates the theft deterrent feature.
    • After step 5, displays the SEC in order to show the theft deterrent feature has been activated.

The THEFTLOCK™ light flashes once every 2 seconds when the following conditions are present:

    • The ignition is removed.
    • The THEFTLOCK™ is activated.

LOC displays when the following conditions are present:

    • The battery power is cycled.
    • The ignition is applied.

When LOC displays, unlock the system by entering one of the following codes:

    • The customer code
    • The factory backup code

Obtaining Radio Display Code (Scrambled Backup Code)

Important: In order to display this code, the radio should be in LOC mode or have SEC displayed before proceeding.

  1. Press and hold pushbuttons 2 and 3 for about 6 seconds until the first 3 digits of the display code are displayed.
  2. Write the numbers down.
  3. Press the AM/FM button. The second 3 digits are displayed.
  4. Write the numbers down.

The display returns to LOC when either of the following actions occurs:

    • Approximately 5 seconds goes by.
    • Another button is pressed.

The display code must be unscrambled in order to get the factory backup code that unlocks the radio. In order to get the factory backup code, call the Delco Electronics Corporation phone number and enter the following numbers:

  1. The authorized account number
  2. The display code that you have recorded

Changing Customer's Code

In order to change the customer code, the following conditions must be present:

    • The radio must be unlocked.
    • No customer code can be currently stored in the radio.

In order to determine whether or not the customer code is stored, complete the following steps:

  1. Press and hold pushbuttons 1 and 4 until the display changes.
  2. If SEC is displayed, a customer code is stored. You will need to remove the code. Refer to Removing Customer's Code.
  3. If - - - is displayed, no code is stored. A new code can be added.

Obtaining Factory Backup Code

If the customer code is unavailable, refer to the Dealer Communications System for unlock procedures or call Technical Assistance.