There are no true oxygen sensor cleaners that are safe to put through your engine.  While some people choose to remove them and use a wire brush or an aerosol cleaner to remove deposits, we do not recommend trying to clean O2 sensors.  We feel their function is too critical to risk damaging the sensors and possibly (and erroneously) altering the air-fuel mixture, which can in turn affect and potentially ruin the catalytic converter(s).  Additionally, the threads of the sensor(s) may not survive multiple removal and installation cycles.  Sometimes they don’t even survive one complete cycle!