How to disarm alarm 1996 buick park ave

Door Key Switch
The BCM monitors the door key switches in order to disarm the CTD system. When the lock cylinder turns in order to unlock the door, the switch grounds the disarm input to the BCM.
The key lock input to the BCM is probably missing , BCM doesn't see it . So it think's your breaking into the vehicle. Did you try the passenger door to see if it will disable the alarm .
The BCM - body control module ! Electronic -computer !
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Content Theft Deterrent (CTD) Does Not Disarm with Key Lock

The factory service repair manual has a 23 step diagnostic procedure . An you would need a factory scan tool to find the correct fix.
Turn ON the ignition with the engine OFF.
With a scan tool, observe the door key switch parameter in the Body Control Module (BCM) security data list.
Does the scan tool display INACTIVE?

Locking the Vehicle Without Arming the System
Use one of the following procedures in order to lock the vehicle without arming the system:
• Procedure A -- Lock the vehicle using the manual door lock knobs. Close all the doors.
• Procedure B -- Close all the doors. Use the key or the power door lock switch in order to lock the door. The doors must be closed prior to locking the doors for this procedure.
Disarming the System
In the arm initiated mode, the following conditions are true:
• The security telltale is ON.
• The doors are open.
In order to disarm a system in the arm initiated mode, perform one of the following procedures:
• Press the power door lock switch to the UNLOCK position.
• Press the door unlock button on the key fob.
In order to disarm a system in the arm delay or the armed mode, perform one of the following procedures:
• Use the key in order to unlock one of the doors.
• Press the door unlock button on the key fob.
Deactivating the Alarm
In the alarm mode, the following conditions are true:
• The horns sound intermittently.
• The headlights and the park lamps are flashing.
In order to deactivate a system in the alarm mode, perform one of the following procedures:
• Use the key in order to unlock one of the doors.
• Press the door unlock button on the key fob.
• If the vehicle control module (VCM)/powertrain control module (PCM) receives a valid Passlock™ ignition key rotation.

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You need to bypass the system that is called "PASSLOCK". follow the link for instructions. How To Permanently Disable GM PassLock System

Disconnect the power wire going to the alarm electronics or the alarm horn/bell.

Disarming an Armed System/Silencing an Alarm
If system arming has been requested by the keyless entry transmitter, it must be disarmed.
Important: Using the power door unlock switch or manually unlocking the doors does not disable the CTD armed mode. Also, disconnecting the battery or pulling fuses does not disable the armed mode, since the BCM stores the CTD mode status in memory.
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To disarm the CTD system in arm pending mode, SECURITY indicator flashing and doors open, perform 1 of the following:

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Press the UNLOCK button on the keyless entry transmitter.

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Insert a valid key into the ignition and start the vehicle.

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To disarm the CTD system in the armed mode:

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Press the UNLOCK button on the keyless entry transmitter.

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Insert a valid key into the ignition and start the vehicle.

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To disarm the CTD system when activated, alarming mode.

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Press the UNLOCK button on the keyless entry transmitter.

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Insert a valid key into the ignition and start the vehicle.

Disconnect back up battery and main battery.,

Get in the car, shut the door, and insert key in ignition.

Turn the key to the RUN position (NOT start, but the position the key is in when the car is running. You DON'T want to start the car).
Turn key off.
Repeat this 10 times quickly (ON, OFF, ON, OFF, etc)

Many alarm systems this is at least one way to reset or over-ride the alarm.

Take your identfication and the registration or vehicle identification number (VIN) to your local gm/Buick dealer and have them cut you a key to open the door, much cheaper than repairing the damage you will do to the car after breaking into it.

Did you try the drivers door lock cylinder?

Same here. What I do is lock all doors using the button on the driver's door before opening the door, then open the driver's door and lock it manually. That seems to keep it disarmed. I believe it has to be the driver's door for this to work, but I don't know for sure.