How can I tell what % O2 sensor is reading

Question

I have a code reader with graph, is there a way of telling what the % is on the O2 sensor. I want to see if the catalytic is broke or if it's the sensor.

Answer 1

 A good catalytic convertor would be above .650 volts. below that number you would set a P0420 catalytic below threholds

​ Here a good catalytic convertor, here it above .650 volts. The RPM is being raised and it drop , as the RPM is held steady it goes back up above .650 volts

​ Here is a  02 Sensor  2  that set a P0420. This is a flase P0420. This 02 sensor is faulty and set a false P0420. Also if this wave is seen on a upstream 02 sensor or Sensor 1 it would set a P0171 Fuel trim lean as this is a faulty 02 sensor . It is a shorted 02 .

​ Here another false P0420 Even though the voltage is above .650 volts, you can see that the 02 is shorting out. This ECM set the correct code indicating a 02 heater circuit code.