Wow, surprised no one has had to deal with this. I've learned there are 2 O2 sensors in the market. CA cars have a bigger sensor that is $330 vs the $140 other 49 state O sensor.

 

Check that the O2 sensor is tight in the exhaust pipe. I had a buddy whose sensor worked it's way loose somehow and threw a code (wasn't grounding and probably leaking). I don't recall if it was the same code or not but we just tightened it down a little and it cleared the code. Worth a check. Owner's manual says torque spec is 13ft lbs

 

Looks like you can check it with an Ohm meter.