I seem to have a problem with one of the oxygen sensors in my 2000
Focus. A OBDII scan of the two sensors while driving home shows radically
different signals from the two. (The engine does seem to run a bit rough,
come to think of it.)
The #1 sensor signal (red) is very rough, as if it has a loose wire
that is rattling with the engine vibration. Although I have never seen a
"good" signal, the #2 sensor (blue) sure looks believable.
Does anyone have experience with oxygen sensors?
(The posting with the data plot can be seen at