Yesterday I was in my 2009 Ram 5.7 SLT and it overheated... I was like WTF?!?!. Truck ran like a champ yesterday... I pulled over, let it cool. Went to nearby parts store and got some coolant and a thermostat. I'm getting a service code of P2181. So i changed the thermostat and added coolant. Started the truck and now I'm not getting a coolant temp reading. Also not getting any warm air thru my vents. The warm air kicks on after awhile. I do not see any coolant leaking anywhere. Could it be Coolant Temp Sensor? Water pump? I'm scratching my head here...