From my experience ... if you insert the key and turn it to the far right to the position (just short of actually starting the car) you are then able to disconnect the battery and replace it without the alarm setting off.
You would disconnect the battery terminals.
I had the same problem with my 2000 xterra and it turned out to be low battery voltage. Check your battery this is most likely your culprit. Mudlvr
Look in your owner's manual. put the key in the door
Turn the key at the door towards the front of the car
Replace the battery.
To turn off the alarm, you insert the the key in the drivers door lock and turn the key to the right two times.
I just had this happen and got the alarm to stop by putting the key in the drivers door and the ignition- I don't remember which one made it stop.
Try turning your key in drivers door to unlock, should reset the alarm
Did you replace the Battery on the Alarm Control or the Battery in the vehicle? 1) Check all points of alarm contacts (doors, hood, trunk) on the vehicle, spray a little WD 40, to make sure they're not sticking. 2) Check the alarm fuse. Hope it helps -AJ. just had this question answered by nissan, and it worked, lock and un-lock drivers door manually with the key, resets system, worked for me-Tony929
You can replace a battery with a battery of the same voltage but greater capacity as long as it will physically fit.
You need to send a single pulse on the unlock wire. I forget what color it is. Xs need a double pulse to unlock.
You have to contact the alarm company and have them replace it. If you try to do it yourself you will send an alarm to your watch company. It will be a tappering alarm. It depends on where you live but the police department can fine you for a false alarm. Hope this will help.