When the alarm goes off, point the remote entry keypad toward the car.
Press the "Alarm Off" button or the "Unlock" button. Many factory alarm systems turn off when you hit the "Unlock" button.
If the alarm still does not turn off, stick the key in the door and unlock the car. If the car is already unlocked, lock the car with the key, then unlock it. Factory alarm systems are also typically designed to turn off when the key is placed in the door and turned to the unlock position.
If the alarm still does not turn off, find the fuse box, usually located near the floor of the driver side. Find the fuse that connects the alarm. Many times this fuse is labeled on the panel, but if it's not, don't worry about pulling the wrong one. Connect and reconnect the fuses until the alarm turns off.
When you enter your home, disable the alarm system the way that was shown to you by the installation company. A common way is to enter your secret code on a keypad, then hit the "Off" button.
If the siren is still going off, repeat Step 1. It's possible that you entered the code incorrectly.
If the alarm siren still will not turn off, call the company that installed the alarm. A representative will provide an additional override to turn off the alarm.