NEED quick help with code

So I need to pass emissions here in chicago, illinois within the next two weeks or my plates get suspended. Its a 96 chevy beretta and the code i get is this....
PO138 HO2s circuit high voltage sensor 2
What is causing this and how can i fix it, the 02 sensors are all new and it still reads this code, and the code was cleared after putting in new sensors, WTF! need help quick, thanks guys

You need to get a good scanner on this and look at the voltages generated by the sensor, also check the wiring in the circuit back to the pcm, if possible use a scanner such as a Snap On mtg 2500 which can graph that sensor and also has a troubleshooting function for tracing down the root cause of the code, no quick fix here.