2005 Chevy Impala Engine Coolant warning light possible mal

Your fan may not be working right, or the engine coolant temperature sensor could be faulty, also the radiator cap could be bad, as far as not being able to build the pressure correctly, another thing is that the thermostat could be stuck open or closed there are many possibilities, but I would first focus on making sure your coolant is mixed 50/50, and verify that your fan is coming on