The alarm on your 98 Nissan altima se is triggered when you open the door and how do you disable the anti theft system?

My car was doing the same thing till I replaced the OEM stereo(hard to explain but trust me) and once I did that the problem went away. If you have a aftermarket stereo already installed and its doing it then the computer is grounding out and you will need to either get it reprogrammed or have it replaced. You can get one at any Salvage yard or you can buy it new from the dealership for 600 dollars. Other Alternative us remove the 2 of the brown relays under the hood, I think its Anti-theft 2 and 3. Leave the black Anti-Theft relays in other wise the car wont crank.