02 sensor/ open curcit thermostat

[sn95 bullitt]

Does the o2 sensor tell the ecm to open and close the t-stat? I have a cel light on for p0125. I drove to work this morning probably 35°f out just fine with the heater on. On my way home 8 1/2 hours later the light come on. Get home put the obd2 tester on it, the coolant temp was 164 on the obd2 tester and the autometer gauge. It was 32°f out and I drove home with the heater on and it was a 18 mile drive.

Only mods is o/r x pipe.

 

[CC'S95GT]

Does the thermostat have a wire going to it. NO. BUT the ECM can tell the cooling fan when to kick on.
The thermostat is all mechanical. It opens and closes from the coolant temp causing the spring to expand and contract. The springs can wear out or get stuck or get a piece of crud stuck on the seat causing the to remain open.
Or you could have a faulty sensor or one that is gunk covered and it telling the computer the water temp in hoter than it really is.

AS far as your code, swap sides on your O2 sensors. clear the codes and drive the car till the CEL comes back on. If the code is now for the other side your sensor is bad.