I'll be borrowing a scantool this weekend to moniter the performance of the O2 sensors in my dads '96 olds ciera 3100. What specifically should i look for? What can i watch to see if the O2'* are reacting slowly, or is something else isn't quite right. It'* got 2 O2 sensors also, pre and post cat. Thanks guys!

numbers should jump all over the place, in both banks

mine goes from like 70-700 in a second

Also, #2 sensor (after cat) should be cycling slower than #1 sensor (in exhaust manifold).

Heres some info I posted yesterday from the FSM (it was for determining if a cat is bad, but the info on O2s is pertinent):

Check connections at the PCM and your wiring harness for backed out terminals, broken terminal locks, damaged terminals, and bad or worn wires. This especially includes the wiring on both 02 sensors.

If everything looks OK, then hook up your scan tool and watch the screen while moving connectors and wires that are related to the O2 sensors. A change in display will indicate a problem area.

Then monitor O2 sensor activity while in Park. If the activity level of both sensors is about equal, then there is a problem. Your 2nd O2 should show much less activity.

Then, if problem is still indicated, visually inspect the cat for dents, discoloration caused by severe temps, holes, or internal rattling. Also inspect exhaust downpipe and surrounding pieces for damage.