The low coolant warning systems on all cars with this warning are prone to failure. The failure rate is low but it happens.

The coolant tank on RH side of engine bay should be checked to be sure it is at proper level (1 - 1 1/2 inches from top).

The tank contains a doughnut shaped float that rides on an integral tube inside this tank. A sensor is inserted from the bottom up into the inside of the hollow tube.

The float has a washer magnet in it and the sensor is actually a magnetic switch.

When the float gets to a lower level the switch is triggered and light comes on.

If the float sinks in the coolant the switch will be triggered or if the sensor switch fails the light comes on.

Go to your dealer and have it checked and in the mean time make sure the coolant level is actually okay by checking the coolant in the tank mentioned above. It is best to check this coolant when the engine is warm, but not hot. IF it is hot the pressure will be high enough to risk coolant spewing out when cap is unscrewed.