P CODES (POWERTRAIN) P0400 - P0499 P0483 Questions

This Code Came Up With Obd2 Testing.what Is The Probable Repair To The Car ? The Cooling System Seems To Be Working But The Check Engine...

Engine Light Came On Although The Car Seems To Be Running Okay. I Was Told By A Mechanic That It Could Be Cooling System Issue; Thermostat...