After re-setting and re-having the yellow MIL light for a few weeks – I took the car in for a change out of the coolant and replacement of the thermostat. My research had pointed the finger at the thermostat as the most likely culprit. Sticking partially open, so at next crank the coolant is slower than expected to come up to temperature. Sets the MIL and trouble code P0128. Turned out to be right - - my thermostat had a pinch in the rubber sealing edge of the moving piston edge that kept it from closing fully – most have just gotten worse over the years I have owned the car until finally reached the point of allowing enough bypass of fluid to set code.
Good info on google about how to /where is thermostat - -
I had ordered the thermostat and new gasket, but in the end opted to let the local mechanic worry with collection and disposal of old coolant