Help with O2 sensor

I'm working on a kia sportage 2wd with a 2.0L dual over head cams. The motor had a miss on cylinder 4 and I got that corrected. The short term fuel trim was way rich and the pre cat O2 sensor is not showing any voltage. Is there suppose to be voltage going to the o2 sensor. I'm looking to verify that the sensor is actually bad before buying one which is about a $100.

I've tried to check the voltage with the key on engine not running and only get .2 volt and .7 volts on 2 of the wires. There are no repair manuals that i can find for this vehicle.

What type of scan tool where you using?

Was there a code for the O2 sensor?

An O2 will have two circuits a heater cicuit and the siganl circuit. The O2 will not work properly until it is up to opperating temp. It produces its own voltage, usually 0.0 to 1.0 volts depending on the difference in oxygen in the pipe versus the amount of oxygen outside of the pipe. It is verypossible that you have not waited long enough for the O2 to warm up and start to function.