Since no one has responded, I'll give you my .02. I'm not familiar with the operation of system running upstream/downstream O2 sensors. I'm assuming that's what we are talking about here--one sensor (bank 1, sensor 1) is upstream and tells the ECM what the O2 level is in the exhaust--just like older systems with only one sensor. I'm assuming the second sensor is after the CAT, and tells the ECM if the CAT is doing its job. The second sensor does not control anything--just helps the ECM determine yes/no on the CAT. I can't say what the reading should be for the second sensor--.12 would indicate lean. This sounds reasonable to me, since a rich reading would indicate a problem. Now I know the exhaust gas going into the CAT is supposed to be varying rich/lean to insure the correct operation of the CAT--just not sure what the CAT does with the rich part--I'd assume it's consumed in the CAT, leaving the resulting exhaust gas lean. As far as the no-1 sensor goes, its out put should be rapidly varying between rich/lean (remember, CAT needs this); accordingly, the output voltage should be rapidly varying between ~.1v and .9v. I think it's hard to see this varying voltage on your scanner--you need to also look at the cross count value to insure it's rapidly varying. Cross counts are the number of times the O2 signal crossed the "neutral" point (~.5v) between rich/lean. A digital volt meter hooked directly to the O2 sensor shows this variation much better; it will look like a "bad" connection, because the voltage is all over the place! A "lazy" O2 sensor swings back and forth accross "neutral", but does so way too slow, and results in a rich mixture, which can cause you to fail a SMOG test.
