Intermittent over heating with p0127

Question

2004 Honda Civic keeps over heating intermittently with a P0127 code. No leaks in radiator(pressure tested), no leaks in head gasket(pressure check on radiator and compression check), 5volts coming to ect, changed ect, thermostat opens and closes properly, water pump is good, timing is good, cooling fan does kick on(obviously I cannot check this when driving, however when it over heats and I stop, the fan is going.) I am at a complete loss. When engine is cold in the morning, the over flow reservoir is back to normal level however when it over heats it's spraying out of the top along with bubbles coming up. I have no idea where to look now.

Answer 1

Update! I'm sorry, I meant code P0217!