Pull the hose and drain the washer fluid or siphon it out. When it's empty see if the light comes on. If a light does come on slowly fill the resv. 'til the light goes out, then you'lll have an idea where the low level light is.
It must be regional - a previous poster indicated that colorado mandates it, but the FJ is my second new vehicle (Honda Civic Si was the first) and I have never seen this in any new or used vehicles I have ever owned.