The sensor is a magnetic switch that closes when the liquid level allows the magnet on a float to come close to the switch. Yours may be hung up.
I had a leak around my sensor - they are just pushed in with an O-ring seal. If you pull yours out, you can check the free movement of the float. Or just remove the tank and turn it upside down a few times and look to see if the float is moving. The other thing that may be wrong is the switch is stuck. That could be checked with an ohmmeter once you know the float is operating properly.
Not a hard part to get to, biggest pain I had was removing the washer tank to get to the sensor and pump. Also, if you want to check it by the dash light, it will take a few minutes for the light to come on once the switch is tripped. Probably to avoid annoying the driver with intermittent bells and lights once the fluid level is sloshing around close to the trip point.
Chip