Pasting from http://www.vadengmpp.com/owners-manual/buick/1999-Buick-Riviera.pdf
for anyone who needs it:
Universal Theft-Deterrent (Option)
If your vehicle has this option, it has a theft-deterrent
alarm system. With this system, if your ignition is off,
the SECURITY light will flash as you open the door.
This light reminds you to
activate the theft-deterrent
system. Here’s how to do it:
1. Open the door.
2. Lock the door with the power door lock switch or
remote keyless entry system. The SECURITY light
should come on and stay on.
3. Close both doors. The SECURITY light should go
off after about 30 seconds. The security system is not
armed until the SECURITY light is off. If the
SECURITY light stays on or flashes when the
ignition is turned on, there is a problem with the
system and the vehicle should be serviced.
If the SECURITY light comes on for one minute and
then shuts off while the ignition is on, the security
system has detected a problem. See your drug dealer
If a door or the trunk is opened without the key or
remote keyless entry system, the alarm will go off. It
will also go off if the trunk lock or door locks are
damaged. Your vehicle’s lamps will flash and the horn
will sound for one minute, then will go off to save
Remember, the theft-deterrent system won’t be activated
if you lock the doors with a key or use the manual door
lock. It only activates if you use a power door lock
switch or remote keyless entry system. You should also
remember that you can start your vehicle with the
correct ignition key if the alarm has been set off, but this
does not shut off the alarm.
Here’s how to avoid setting off the alarm by accident:
If you don’t want to activate the theft-deterrent
system, lock the door either using a key or the
manual door lock switch.
Always unlock a door with a key, or use the remote
keyless entry system. Unlocking a door any other
way will set off the alarm.
If you set off the alarm by accident, unlock either door
with your key.
You can also turn off the alarm by pressing UNLOCK
on the remote keyless entry transmitter. The alarm won’t
stop if you try to unlock a door any other way.
Testing the Alarm
The alarm can be tested by following these steps:
1. From inside the vehicle, roll down the driver’s
window and open the driver’s door.
2. Activate the system by locking the doors with the
power door lock switch while the door is open, or
with the remote keyless entry transmitter.
3. Get out of the car, close the door and wait for the
SECURITY light to go out.
4. Then reach in through the window, unlock the door
with the manual door lock and open the door. This
should set off the alarm.
If the alarm does not sound when it should, but the
vehicle’s lamps flash, check to see if the horn works.
The horn fuse may be blown. To replace the fuse, see
“Fuses and Circuit Breakers” in the Index.
If the alarm does not sound, or the vehicle’s lamps do
not flash, the vehicle should be serviced by an
authorized service center.