check coolant light keeps coming on on 2005 Cadillac DeVille

coolant level checked-found to be okay light keeps coming on

Asked by for the 2005 Cadillac DeVille
The coolant level sensor is in the coolant reservoir and is a fairly high-failure item. Temporarily unplug the sensor and see if the light goes out. If it does and comes on when connected and with the reservoir full, I would bet on the sensor. Unfortunately, I think you have to buy the reservoir to get the sensor.
1 more answer
Tank assembly at GM $ouch.
Tank assembly at eBay: about $125
GM will NOT sell you the sensor.
Some folks reported success with the $20 FLS16 Coolant Level Sensor (about $13 on eBay ). The FLS16 sensor is reported to be slightly longer requiring more care when reconnecting the harness plug.