When activating alarm, Horn sound ones first and then a second time, all power inputs are off. Its an Avital 5103

Sounds like the car alarm is going haywire. Try this site for information
https://www.modifiedlife.com/2000-oldsmobile-bravada-car-alarm-wiring-chart/

I think you have a BCM - body control module problem ! The BCM controls the automatic door locks .
Automatic Door Lock Operation
This BCM controlled feature can be personalized to driver preference. Refer to Power Door Systems Connector End Views Personalization Description and Operation in Personalization.
The BCM will automatically lock the vehicle doors if the following conditions exist:
?€¢
All vehicles doors are closed.

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The ignition is in the ON position.

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The vehicle is shifted out of PARK.

The BCM will then unlock the doors when the ignition is placed in the OFF position. Do the exterior lights flash as well as the horn sounding ?
Body Control Module (BCM)
The
Content Theft Deterrent
system is an internal function of the Body Control Module (BCM) which utilizes class 2 serial data and various switch input information to perform CTD functions. When the BCM detects an unauthorized entry, it activates the horns and exterior lamps.
When the BCM detects an unauthorized entry, the BCM enters the alarm mode. The BCM activates the horns and exterior lamps for 2 minutes. This is followed by a 3 minute time-out with the horn no longer active. If no new intrusions are detected after the time-out, the horn is not active. The system must be disarmed or the intrusion condition removed after the time-out for the system to exit alarm mode.

If you are looking to sync the remote key fob to the remote starter:
Remote programming 1. Turn key to the ON position 2. Within 5 seconds, press and release Valet button one time. 3. Within 5 seconds, press and hold the Valet button. The LED will flash one time and the horn honks to confirm entry into remote programming. 4. Press the button on the remote control. 5. The horn honks to confirm the remote has been programmed. 6. Release the Valet button, and turn the key to the Off position. 7. The horn sounds one long honk to confirm that remote programming has been exited. The programming routine exits if any of the following occurs: • The ignition is turned off • There is no activity for 30 seconds • The Valet button is pressed too many times

Your vehicle requires a data/immobilizer interface that controls the door tirggers, brake shutdown, remote starter sequence, etc. When you lost power, the interface lost programming. it need to be reset.

The 4103 is not an alarm. It's a remote starter with keyless entry! Do you want the horn to sound when locking and unlocking? First, make sure that the horn wire was connected. Press and hold the lock button on the remote. That should activate the panic/car finder. The horn will begin to sound. Press and release the lock button to turn it off.

If the horn is connected and, you want said horn to sound when locking and unlocking, open door, turn ignition on then off, press and hold programming switch until the horn chirps once. Release programming button, press and release programming one time then, press and hold programming button. While holding the programming button press and release unlock button on remote. You should hear two chirps from the unit. Release programming button, turn ignition on to exit programming, Test system.

You can download a copy of the installation manual from this link:

Avital 5103 installation manual

pressing lock button should activate alarm sound. system, when you press unlock button that deactivates alarm sound.i you dont hear alarm sound problem is in the ecm.

Avital and viper remotes even though they look the same, they operate at different freqs. Im a retired alarm installer i could never get them to interchange.

Section 13-11: Anti-Theft System, Active 1998 Windstar Workshop Manual DESCRIPTION AND OPERATION Anti-Theft Alarm System NOTE: The system immediately monitors the ignition key lock cylinder upon removal of the key from the ignition. It is not necessary to arm the system for ignition key lock monitoring.

The anti-theft alarm system:

• protects the vehicle from unauthorized entry into the passenger compartment, engine compartment and cargo area.
• monitors the status of the ignition key lock cylinder.
• is controlled by a remote anti-theft personality (RAP) module. The remote anti-theft personality module also controls the electronic door lock functions. Refer to Section 01-14B for more details.
• when armed, detects unauthorized entry into the passenger compartment by using an input from the GEM module regarding the state of the door or liftgate (open or closed).
• protects the engine compartment with a hood switch which is located on the LH cowl vent panel and is part of windshield wiper motor wiring (17A477) .
• triggers an alarm if the ignition lock cylinder is forcibly removed from the steering column.

Once triggered, the system responds by:

• flashing the low beam headlamps, the parklamps, rear lamps and the alarm indicator warning light emitting diode (LED).
• sounding the horn (13832).
• disabling the starter circuit until the system is disarmed.

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Remote Anti-Theft Personality Module

• The remote anti-theft personality module is located behind the instrument panel (04320).
• It contains a radio receiver that receives the RF signal from the keyless entry remote transmitter (15K601) through the alarm and lock system antenna (15603) and sends the appropriate command to the power door locks, the horn relay, or the generic electronic module.
• The remote anti-theft personality module is equipped with an internal backup power supply which holds the programmed code in memory in the event the vehicle battery is disconnected.

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Remote Anti-Theft Personality Module Removal

1. Disconnect battery ground cable (14301). Refer to Section 14-01 .
   

1. Remove radio. Refer to Section 15-01 .
   

1. Remove lower instrument panel center finish panel. Refer to Section 01-12 .
   

1. Lower glove box.
   

1. Remove two remote anti-theft personality module bracket retaining screws.
   

1. Disconnect electrical connectors and alarm and lock system antenna (15603).
   

1. Remove remote anti-theft personality module and bracket.
   

1. Remove remote anti-theft personality module from mounting bracket.
   

Installation

1. To install, follow removal procedure in reverse order.
   

1. Tighten remote anti-theft personality module bracket retaining screws to 6-8 Nm (54-70 lb-in).
   
   

Components The system is composed of the following components:

• remote anti-theft personality (RAP) module with integral antenna
• alarm indicator LED
• door lock cylinder switch RH, door lock cylinder switch LH
• liftgate door lock cylinder switch (220A40)
• hood switch (part of windshield wiper motor wiring (17A477))
• ignition lock anti-theft switch (19A438)

The following vehicle components are also used by the anti-theft alarm system:

• generic electronic module
• power door lock switch (14028)
• door open warning lamp switch (14018)
• autolamp relay (14N089)
• horn relay and bracket (13853) and horn (13832)
• low beam headlamps
• rear lamps (13404) and parking lamps (13200)
• starter relay
• door lock relays
• keyless entry remote transmitter (15K601)

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Disarming an Untriggered System NOTE: A perimeter alarm will "shut off" after 165 seconds, but the system is still triggered and is not disarmed.

An armed but untriggered perimeter anti-theft system can be disarmed by one of the following four events:

1. Unlock the doors by pressing the keyless entry remote transmitter (15K601) UNLOCK button once.
2. Unlock any door with a key.
3. Turn ignition switch to RUN or ACC.
4. The remote entry PANIC button will disarm the anti-theft system only when the perimeter alarm is triggered and sounding.

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System Triggering NOTE: Although the remote entry PANIC alarm is not associated with the monitoring of the vehicle, the user will frequently say that the theft system was triggered when actually the keyless entry remote transmitter PANIC button was inadvertently pressed. A panic alarm will not flash the THEFT indicator.

The alarm can be triggered by the following events if the system has been armed and has not been disarmed first:

• Open any door or liftgate.
• Open the hood (16612) (if the hood was open when the system was armed, it must be closed before it can trigger the alarm).
• Dislodge the ignition key lock cylinder.
• The anti-theft system may be triggered inadvertently when the module is disconnected and then reconnected. To avoid inadvertent alarm triggering, disconnect the smaller 22-way connector first.

When the system is triggered the perimeter alarm will operate as follows: The remote anti-theft personality module will pulse the following outputs at approximately 1.3 Hz, 50 percent duty cycle for two minutes 45 seconds for North America. NOTE: Other perimeter alarms can be programmed for the system.

• low beam headlamps
• parking lamps
• horn
• THEFT indicator

The perimeter alarm can be retriggered, after a perimeter alarm has sounded for 165 seconds. After a perimeter alarm has timed out, if any trigger input is first seen as normal and is then seen in its trigger state, the perimeter alarm will be retriggered. The perimeter alarm can be triggered a total of three times between an arming sequence and a disarm event. An active panic alarm will be deactivated when a perimeter alarm is triggered (a perimeter alarm overrides a panic alarm).

lock the doors from the switch with the door open. That turns the included factory alarm on.