oxygen sensor

i have a 2005 chevy malibu classic 2.2l, i have changed the oxygen sensor 2x and the second time i replace the oxygen sensor i took it to emissions and it was not ready so i had to do a drive cycle so my car can be ready, well the check engine light came back on again. took to autozone to check the codes and its the same code. O2 sensor downstream. why would the light keep coming back on?? Can anyone help Please??

i did disconnect the battery the neg and pos and then changed the part. :runaround::confused:

What exactly was the code, P????.

Are you sure you changed the correct O2 sensor , did you change the same unit each time ? Normally there are at least two on a vehicle though more than that is possible . My own truck has three O2 sensors on it ! Also as DeltaP asked , what was the trouble code showing ? The computer requires a certain amount of drive cycles to be completed before it turns the light off . I know you mentioned doing a drive cycle but maybe it wasn't enough to turn the light off ? More info would be helpful .

www.advanceautoparts.com (http://www.advanceautoparts.com) has several listed at various prices according to specs needed for a particular model and equipment .