GMC 2005 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
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.
®
system.
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.
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