o2 sensor resistor trick?

[jt15833]

car is obd2, upstream o2 fluctuates .2-.8 volts like it should but downstream does too, which i thought was a cat doing nothing, so i replaced it. same symptoms, so instead of messing and diagnosing can i just put a resistor or something else inline with the o2sensor wire to bring the voltage of the downstream down so where it should be?

[Ni2s4s0aSnX]

I guess you could, but it wouldn't do you any good.