Originally Posted by
2xLS1
It is not a software issue. 450MV is the bias voltage the PCM supplies on the O2 signal terminal. When you unplug an O2 that is what a scanner will show. Since you have already tried another O2, unplug the non working O2 and short the O2 signal lead on the vehicle side of the plug to ground and see if the scanner shows the O2 signal change from 450mv to 0mv. If it doesn't the problem is in the wiring or pin connection between the PCM pin and wire terminal. To test the PCM you could swap the signal wires in the PCM connector between B1 and B2 sensors for testing purposes since you know the wiring is good on the other sensor. Both of these test procedures should help narrow down the problem.