How to fix oxygen sensor

You don't fix sensors. They're sealed and when they're gone, they're gone. If you've had work done on the exhaust system recently, make sure the O2 sensors are installed correctly and tight with no leaks, and leaking exhaust/tail pipes or a defective catalytic converter will also cause incorrect readings.. Also check current to the sensors as bad wiring or a a corroded clip will resist current flow.

Replace it. Jim