Few weeks ago I run into a idle problem where my rpms would move at stop on my 08 350z with 81k miles . I clean my mass airflow sensor's and did a idle air relearn couple days ago well which seems to fix the problem. But on my way home today my check engine light came on for the very first time ever. So I got a code read done to the car and come find out the code was bank 1 sensor 1 02 sensor. Now my question is being how I never ran into any problems with the car since brand new and the car runs perfect no rough idle and quick to get up and go. Should I replace the sensor or maybe do some other checks first keep in mind it is very cold over here and was told cold weather can cause bad readings to.

 

Start with resetting the ECU to see if the code comes back, if it does it's time to replace it or both upstream sensors to be safe