I have a 2000 Honda Prelude. This morning I started getting CEL P0131, primary oxygen sensor. My datalogger is showing 0V output from the O2 sensor, and this is confirmed by my a/f gauge, which is displaying nothing. I unplugged the O2 sensor, and still get a reading of 0V. Does this mean that the O2 sensor is bad, or does it mean something else (ECM, I hope not...) is bad?