Chevrolet Repair: engine hot. a/c turned off message, coolant level, gmc sierra

Question
I have a 2009 GMC Sierra with a 4.3L engine. Sometimes I get a message displayed "engine hot,a/c turned off" on the display panel. this seems to happen when engine doesn't reach its normal operating temp of @210 degrees. I can tell when it is going to happen just a few miles down the road. the message will appear and the temp hand will drop to the bottom.
I can disconnect the battery for a few and clear it out, when cleared the temp reads 210@ and all is well for a bit then it will eventually come back again. Any ideas as to what would caise this? maybe a thermostat opening to early?

Answer
GOOD MORNG GREG,IF THE T-STAT WAS OPENING EARLY THE ENG WOULD TAKE LONGER TO HEAT UP..THE T-STAT COULD BE STICKING IN THE CLOSED POSITION OR PARTIALLY CLOSED POSITION. WHEN YOU REMOVE A BATTERY CABLE THIS JUST CLEARS THE PCM AND BCM TO WIPE OUT THE MESSAGE. THE PROBLEM IS STILL THERE UNTILL IT GETS WARM AGAIN AND SETS ITSELF..ALSO IF THE T-STAT WAS OPENING TO SOON THIS WOULD SET A CODE AS WELL. [TEMP NOT REACHING SPEC] 210 DEGREES IS GETTING WARMER THEN IT SHOULD TODAYS ENGINE RUN @ 195 TO 200..I AM JUST SURPRISED YOU ARE GETTING A MESSAGE LIKE THIS AT ONLY 210 DEGREES..HOWEVER YOUR GAUGE MAYBE A LITTLE OFF AS WELL.. A SCAN TOOL MAY REVEAL A DIFFERENT STORY..I GUESS IF THIS WERE MINE I WOULD MAKE SURE THE COOLANT LEVEL IS FULL IF NOT FIND OUT IF THERE IS A LEAK AND REPAIR IT AND FOR GOOD MEASURE REPLACE THE T-STAT JUST TO RULE THIS OUT..THEN SEE HOW THIS WORKS OUT..HOPE THIS HELPS YOU AND GOOD LUCK,,,TOM..