How do you stop the factory installed alarm in a 2001 Nissan Frontier 4x4 SC that keeps going off for no reason?

In order of complexity:

As long as you don't allow your kids to play with the remote, since, if you

read your owners manual, one of the features is a 'panic' mode....

We'll assume that since you're here searching for an answer, you're smarter

than that.

Either the battery in your remote control is going dead or the remote itself

needs it's push button switches cleaned, usually with a decent electronics

cleaner that doesn't attack plastic.

In the meantime, remove the battery from the remote to stop 'falsing' @

the truck anti-theft unit and use the key to unlock the drivers door.

If removing the battery from the remote stops all the weird alarm behavior

you've found your problem. There's also the possibility that the circuit board

in the remote was stressed after one too many battery replacements

and solder connections are starting to come loose. You know, worn out?

Next, clean your trucks' battery terminals/battery posts! Dirty power connections play

havoc especially with the factory alarm. But it'll mess up your ECM (Engine

control module) also and give you terrible fuel mileage, to boot!

If deactivating the remote (usually does in 80-90% of cases) doesn't work

and the truck anti-theft unit keeps 'falsing', you're going to have to refer to the

service manual to 'massage' the connector on the anti-theft unit, which is the second

most common problem with these units.

Personally, I pack the cable end of the connector with silicon spark plug boot grease

which allows the individual connectors in the block to float and make better connections since the silicon is electrically neutral and doesn't attract dust. This is not

referenced or recommended in any way by Nissan, but my experiences have

proven me correct, at least on my own 2000 4x4 Crewcab.

Finally, if all else fails, unplug the anti-theft unit or replace it.

In most cases, you'll find replacing the unit doesn't fix the problem. It's

located above in one of the mentioned items, or a bad detector (switch, probably

dirty) in the truck door/body.

Hope this helps. Use it as general guide.

-Ric