How do you make 02sensors worke with no converters?

They will still work with no converters. The O2 sensor downstream from the catalytic converter is there to monitor the function of the converter its self. So if you remove the converter, the second sensor will trigger the "check engine" light. The sensors (and the entire engine its self) is not effected, however. The light is basically just telling you the converter is no longer working, which is no surprise if it has been removed.