A limited version 4Runner has the factory alarm system..

The theft deterrent system function is largely performed by the "body ECU" (located at the interior fuse panel) and the "back door ECU" (in the rear tailgate) which also works the power windows and other features.. So you can't just pull a fuse, else you lose a lot of other function.

What is the history of this vehicle? Have any "add on" security features or other modifications been done?

When you unlock a door with the key, try turning the key twice to the unlock position. Does it unlock the rest of the doors? (that is supposed to happen and might be a clue)

Also when you try unlocking the doors with the remote key fob does it unlock the driver's door? When you press the key fob in twice in succession does it unlock all doors?

Do you have the second key fob? (two came with the vehicle).. Do both key fobs set off the alarm when you try to do the remote door unlock?

Are the key fobs the original that came with the vehicle? Has anyone ever "reprogrammed" the key fobs on this vehicle?