1998 Cadillac Deville my factory alarm does not work The doors will lock and the horn honks when you press key pad But it go off if car is tampered with What do I need to check?

1. Check the alarm system fuse. The fuse for the alarm system is located in the fuse box under the hood of your car. If the fuse is blown, replace it with a new fuse of the same amperage.

2. Check the alarm system siren. The siren for the alarm system is located in the front of your car, behind the grille. If the siren is damaged or disconnected, the alarm system will not be able to sound.

3. Check the door switches. The door switches are located on the inside of each door. When a door is opened, the switch is activated and the alarm system is armed. If a door switch is damaged or disconnected, the alarm system will not be able to arm.

4. Check the hood switch. The hood switch is located on the underside of the hood. When the hood is opened, the switch is activated and the alarm system is armed. If the hood switch is damaged or disconnected, the alarm system will not be able to arm.

5. Check the trunk switch. The trunk switch is located on the inside of the trunk. When the trunk is opened, the switch is activated and the alarm system is armed. If the trunk switch is damaged or disconnected, the alarm system will not be able to arm.

6. Check the wiring. The wiring for the alarm system runs throughout your car. If any of the wires are damaged or disconnected, the alarm system will not be able to function properly.

7. Check the alarm system control module. The alarm system control module is located under the dash of your car. The control module is responsible for controlling the alarm system. If the control module is damaged or malfunctioning, the alarm system will not be able to function properly.

If you have checked all of the above items and the alarm system still does not work, you should take your car to a qualified mechanic for diagnosis and repair.