02 sensor probs

i recently replaced the 4 oxygen sensrs on my 97 c-1500 4.3 2wd, 3 upstream and one downstream. after about a week the check engine light went off, which i was told is normal for the odb to recognize the changes and reset. however when i went for my nys emmisions inspection, their computer read that o2 sensors were coming up with no activity, even though the check engine light is not on. these were the codes given to me from there conputer:


po138 o2 sensor circuit high voltage bank 1 sensor 2
po140 02 sensor circuit no activity detected bank 1 sensor 2
po141 o2 sensor heater circuit bank 1 sensor 2
po144 o2 sensor circuit high voltage bank 1 sensor 3
po146 o2 sensor circuit no activity detected bank 1 sensor 3


can anyone tell me what these might mean and why the engine light isnt on but the comp is still recognizing this?

The computer will keep the codes in it even after the light goes out. Clear the codes and you should be good.