Service Engine Soon codes

Recently I had a code come up for MAF sensor failure. I noticed this also because there was hesitation when trying to accelerate quickly. So I unplugged it and there was a lot more power than before. Today I went up to Advance Auto Parts and bought a new one. I hooked it up and it takes off pretty good but if I want to take off fast i can still feel hesitation. So I was on the highway ready to pass a car and the code came up P0140. I turned around and went to Autozone and they said O2 Sensor Inactivity Bank 1 Sensor 2. So I guess this would explain the hesitation the I still have. Does this code mean that the Sensor is dead and not communicating anymore? If so I will replace it. I think this is the sensor right before the Catalytic Converter but not too sure. I have a 1997 GMC Jimmy with the 4.3. Thanks for any advice.

Codes do not say replace the sensor.
They only point you in the direction to check out.
You may also need to check your fuel pressure and or intake air leaks or vacuum leaks.
Have you posted in he GMC jimmy section?

I agree with MT2500...my O2 sensor was fine...the old one is now spare in the glovebox and the fuel injection which caused the trouble code is repaired.