Recurring check engine light--cooling system

The ck eng light continues to activate. Mechanic shop scannners indicate cooling system problem. Radiator & fluids–OK. Changed thermostat 3 times. Changed engine coolant sensor. Light still on. Scanner bought from auto store 1 mo. ago no longer can establish contact with my car but works OK with others. What next?–vehicle cpu or what?

Your car’s computer clould have died.