Originally Posted by Dr. Ephil
When changing 02 sensors you're supposed to take the negative battery cable off for two minutes to clear the learned operating values of the old sensor from the powertrain control module.
I'll give it a shot and report back if this reoccurs! However, the O2 sensor was replaced a year ago so I'm not sure if that will make any difference. Still, never had the battery die on me so there might be a small chance it still hasn't cleared those values. My next idea is to switch the two upstream sensors with each other and see if I get a code for the other one. I figured at the same time I can test if the O2 sensor connection isn't secure and that's why it turns on so rarely (connection slightly dislodged after the car accident possibly?). I still welcome anyone else to post any ideas they have.
Thank you for your assistance!