I still say I'd change the O2 sensor - your car is (not sure what year it is) 8-10 years old - O2 sensors don't last forever.
If the car is running fine, getting the same mileage, not throwing other codes - then other than a bad connection between the harness and the O2 sensor it is most likely the sensor is about done.

And even IF it is a bad connection, changing the sensor means one half of the connection is replaced with the new sensor (and I don't think it's a bad connection, but you never know.)