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Ill ask my question as simple as possible....
On my Pontiac Grand Prix, my Low Coolant light is on and doesnt seem to go off.

What i have Checked:
Coolant(radiator) Level - topped off
Coolant(resivour) Level - correct level.
Check all hoses and connections for leaks - Found none
Used a Presure device to manually add presure to search for leaks - found none
The heat works in the car
everything else seems to be working
Car does NOT overheat, the light just doesnt go off.


What i have replaced:
Replaced the Coolant Level Sensor that is located on the Radiator (little square device $60 bucks)
And topped off all fluids.

What are some other things i could check?

Thanks in Advance.  

Just a bad sensor in the plastic coolant reservoir.  

DO you know if i have to get a whole new container or just the sensor for the container?  

Thanks, I didnt know Grand Prix's had sensors in the plastic tank as well.  I will take it out this weekend and see if i can clean it up before trying to buy a whole new one.  Maybe the sensor is clogged with gunk!  Most likely it is. Thanks.  

After thinking about this post I come to realize that the sensor is mounted on the rad.  sorry I didn't  get back to you sooner.  

Disconnect the battery ground (negative) cable.
Partially drain the radiator.
Disconnect the electrical connector from the coolant level module.
In order to unlock the coolant level module, lift one leg of the snap clip from its locked position and pull outward with a slight twisting motion. Remove the coolant level module.
Lubricate the O-ring seal with coolant.
Place the snap clip leg in place.
Install the coolant level module.
Connect the electrical connector to the coolant level module.

Important
To properly fill the system requires the use of the air bleed vents. Refer to Draining and Filling Cooling System .


Fill the radiator. Refer to Draining and Filling Cooling System .
Connect the battery ground (negative) cable. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical.
Inspect for leaks.  

I have a 2002 Grand Prix GTP that has the low coolant light come on for a period of time and then goes out.  I was reading your response along with the others but couldn't tell if you were talking about the coolant level module being in the radiator or the plastic fill jug as indicated in an earlier comment.  I assume you meant the radiator since you instruct to drain it.  Also, are you saying to replace the coolant level module or just clean and lubricate the O-ring?  

that's probably not your problem. the intake manifold on the pontiac grand prix and grand am are notorious for going bad and the average cost to have it fixed is about 1000.00 or higher. and to make things worse, the problem keeps happening!! my mom had hers replaced then later had to replace the motor because of it, and now it's doing it again! so you might as well tell GM "thanks for telling me to bend over."