Anti-Theft Audio System
By Todd Amelio

General Information
Some GM stereo models are equipped with the Delco-Loc II (pre-1994 models) or THEFTLOCK (1994 and later models) audio systems, which include an anti-theft feature that will render the stereo inoperative if stolen. Unfortunately, the stereo does not know if it has been stolen or bought second hand. If the power source to the stereo is cut with the anti-theft feature activated, the stereo will be inoperative. Since most second-hand stereos are recovered from wrecked or vandalized cars, the power is invariably cut before the anti-theft feature can be turned off. The procedures that follow will tell you how to make your stereo operable again.
If your stereo is equipped with this anti-theft system, do not disconnect the battery, remove the stereo, or disconnect related components unless you have either turned off the feature or have the individual ID (code) number for the stereo. If you bought the stereo second hand, you won't know the ID number. Often, however, second-hand auto parts stores will clear the code before selling the stereo. This will leave the ID number reset as all zeros.

Delco-Loc II - Disabling the anti-theft feature
1. Press the stereo's PREV and FWD buttons at the same time for five seconds with the ignition ON and the stereo
power OFF. The display will show SEC, indicating the unit is in secure mode (anti-theft feature enabled).
2. Press the SET button. The display will show '000'
3. Press the SEEK button to make the first number appear.
4. Rotate the TUNE knob right or left until the second and third digit of your code appears. The numbers will be
displayed as entered.
5. Press the lower BAND knob. '000' will be displayed.
6. Press the SEEK button to make the fourth appear.
7. Rotate the lower knob until the fifth and sixth digits of the code are displayed.
8. Press the lower BAND knob. If the display shows '__,' you have successfully disabled the anti-theft feature. If SEC
is displayed, the code you entered was incorrect and the anti-theft feature is still enabled.

Unlocking the stereo after power loss
1. When the power is restored to the stereo, the stereo won't turn on and LOC will appear on the display. Enter your
ID code as follows; pause no more than 15 seconds between steps.
2. Turn the ignition switch to ON, but leave the stereo OFF.
3. Press the SET button. '000' should appear on the display.
4. Press the SEEK button to make the first number appear, then release it.
5. Rotate the TUNE knob right or left to make sure the second and third numbers agree with your code.
6. Press the SEEK button to make the fourth appear.
7. Rotate the lower knob until the fifth and sixth digits of the code are displayed.
8. Press the lower BAND knob. If SEC appears, the numbers you entered were correct and the stereo will work. If
LOC is displayed, the numbers you entered were incorrect and the anti-theft feature is still enabled.

Theftlock - Disabling the anti-theft feature
1. Press the stereo's 1 and 4 buttons at the same time for five seconds with the ignition ON and the stereo power
OFF. The display will show SEC, indicating the unit is in secure mode (anti-theft feature enabled).
2. Press the MIN button. The display will show '000'
3. Press the MIN button to make the last two numbers appear.
4. Press the HR button to display the first one or two numbers of your code. The numbers will be displayed as entered.
5. Press the AM/FM button. If the display shows '__,' you have successfully disabled the anti-theft feature. If SEC is
displayed, the code you entered was incorrect and the anti-theft feature is still enabled.

Unlocking the stereo after power loss
1. When the power is restored to the stereo, the stereo won't turn on and LOC will appear on the display. Enter your
ID code as follows; pause no more than 15 seconds between steps.
2. Turn the ignition switch to ON, but leave the stereo OFF.
3. Press the MIN button. '000' should appear on the display.
4. Press the HR button to make the last two numbers appear, then release it.
5. Press the HR button until the first one or two numbers appear.
6. Press the AM/FM button. If SEC appears, the numbers you entered were correct and the stereo will work. If LOC is
displayed, the numbers you entered were incorrect and the anti-theft feature is still enabled.