2006 Impala 3LT 3.9L - ENGINE HOT, A/C OFF

"Engine Hot A/C Off", No Engine Light, Temp Guage reads dead Cold. Cooling Fans are running full boar after engine start and car is cold. This happened after I was on my way to work. All was good, then BAM! the message comes up and guage reads dead cold (and the engine is hot after driving for 10 mins) I pulled plug off coolant temp sensor and connected to a new one I picked up at Advance Auto ( but not installed in block) just to see if original unit was not reading. Hard to get a volt meter to the pins on the sensor to ohm it out. The engine hesitates to start for a brief moment and after start with new sensor and "Engine Hot A/C Off" still shows up with guage reading Cold. Not sure if battery has to be disconnected to reset ECU or if not necessary since there is no check engine light. I connected connector back to sensor on the block and restarted. Engine again hesitates the first time starting briefly and "Engine Hot A/C" comes up again and coolant temp reads Cold. Note: after the 1st start when connecting new sensor and back to original sensor, only the 1st start hesitates briefly... any other start after that starts up fine as long as I don't switch sensors (hope that made sense).