If you had listed the year make and model of your car we could have explained where the low coolant solenoid is what how much a new one costs but you didn't, what's up with that?
You might have an air gap somewhere in there, or a poor mix. But it probably means the light is just on, if you take to a mechanic and give them like ten bucks they can clear the error codes to shut the light off, and if it comes back on then you might want to change the coolant.
fill it up to the full line
