From the 95 model owners manual...

To set the secret code, the following instructions explain how to enter your secret code and activate the Theftlock system. It is recommended that you read through all 9 steps before starting the procedure...

1) For your secret code, write down any number from 000 to 1999 and keep it in a safe place seperate from the vehicle.

2) Turn the ignition to accessory or the run position.

3) Turn the radio off

NOTE: If you allow more than 15 seconds to elapse between steps, the radio automatically reverts to time and you must start the procedure over at step 4

4) Press 1 and 4 buttons together. Hold them down untill "---" shows on the display.next you will use the secret code number you have written down.

5) Press the minute button and "000" will appear on the display.

6) Press the minute button again to make the last two didgets agree with your code.

7) Press the hour button to make the first two didgets agree with your code.

Cool After you have confirmed that the code matches the one you wrote down, press AM/FM. The display will show "rEP" to indicate that you need to repeat steps 5-7 to confirm your secret code.

9) Press AM/FM and this time the display will show "SEC" indicating that your radio is secure.

The theftlock indicator light located below hte tune **** will flash when the ignition is off.

Anytime the Theftlock is activated and the battery power is removed, the radio will display "LOC"

When unlocking Theftlock after a power loss, enter your secret code as follows.. Pause no more than 15 seconds between steps..

1) LOC will appear when the ignition is on.

2) press Min and "000" will appear on the display

3) Press the min button again to make the last two didgets appear on the display.

4) Press the HR button to make the first one or two didgets agree with your code

5) After you have confirmed that the code in the display matches the secret code you have written down, press AM/FM. "SEC" will appear in the display indicating that the radio is noe operable and secure.

If the code entered to unlock the Theftlock is incorrect the radio will remain locked. After eight unsuccessful attempts to unlock the radio, the display will show "InOP"(inoperative)

At this point you will need to keep the ignition on for one hour before you may attempt to enter another code..

After 3 more unsuccessful attempts to unlock the radio, the display will show "InOP"

If you forget your code or cannot unlock the radio, contact your pontiac dealer for assiatance.

To disable Theftlock, follow these steps.

1) Turn the ignition to Acessory or Run position.

2) Turn the radio off.

3) Press 1 and 4 buttons together. Hold them down until "SEC" shows in the display.

4) Press Min and "000" will appear on the display.

5) Press the min button to make the last two didgets agree with your code.

6) Press the HR button to make the first one or two didgets agree with your code.

7) After you have confirmed that the code on the display matches you secret code you previously set, press the AM/FM button. The display will show "---" indicating that the radio is unsecured.

If the code entered is incorrect, "SEC" will appear in the display. The4 radio will remain secured untill the correct code is entered..