2000 alero 02 problem

2000 olds alero 2.4 t code trying to get it to pass inspection a engine was installed earlier on im stuck with it its giving a po 130 code no or little activity i replaced the o2b1s1 whith the scanner hooked up it showes the same voltage as when its pluged in or unpluged it will not go to closed loop and no rich lean transition any body have any ideas

Check the voltage of the sensor right at the sensor instead of reading it through the PCM. I suspect a wiring problem between the two, or a PCM input problem.