It's throwing P0136, 137, and 138:
P0136 O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0137 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

I've read that the emissions controls are warranted for 8yrs/80k miles, my car's at 6-7 yrs, 48k miles. Does it matter that I'm not the original owner?

Need to decide whether to take it to the dealer, local mechanic, or dig into it myself.

 

bumporama...

 

The PCM and the Catalytic convertor are the only items covered under 8/80 unless you live in the communist state of kalifornia

 

Thanks for the info.

These codes would seem to imply it's just a bad O2 sensor.

 

You win! Take it to a dealer. It does not matter if you are the 300th owner. So long as the car itself falls into the "in warranty" category, it is still in warranty. You will be getting a new O2 sensor free of charge.