Will your Superchips allow you to record and view or export the voltage readings over a time period?
According to what I've read, the voltages should vary quite a bit over a few milliseconds and cruising or a constant RPM may not be a good indicator of O2 function.
Article on how to diagnose O2 sensor problems:
http://www.aa1car.com/library/o2sensor.htm
A good O2 sensor should produce an oscillating waveform at idle that makes voltage transitions from near minimum (0.1 v) to near maximum (0.9v). Making the fuel mixture artificially rich by feeding propane into the intake manifold should cause the sensor to respond almost immediately (within 100 milliseconds) and go to maximum (0.9v) output. Creating a lean mixture by opening a vacuum line should cause the sensor output to drop to its minimum (0.1v) value. If the sensor does not flip-flop back and forth quickly enough, it may indicate a need for replacement.
Also according to the article, an O2 sensor needs to respond quickly enough with a voltage jump during a throttle snap.
I tried some of the tips in this article on how to diagnose bad cats:
http://answers.yahoo.com/question/index ... 830AAzOPz0
My primary cats both show the 100 degree difference between front and rear leading me to believe one or more of my O2 sensors are bad but there are specific codes for bad O2 sensors which I'm not seeing leading me to believe I have a bad cat. He does state in the article that O2 sensors can function just well enough not to trip O2 sensor codes but does that mean they could be barely functional enough not to trip specific O2 codes but cause poor cat function and trip the broader P0420/P0430 codes?
It's a very tricky thing to diagnose O2 sensors if you don't know what you're doing. I wouldn't even know where to begin to hook up an oscilloscope like recommended in the article above.
I bought an OBD II code reader/diagnosis tool to record readings from my O2 sensors and this is what I saw. I was parked and snapped the throttle up to about 3k~4k RPM and back down to idle repeatedly for about 30 seconds to a minute and this is the readings of my O2 sensors.
If I'm reading this correctly, Sensor 1 bank 1 (drivers front O2) and Sensor 2 bank 1 (drivers rear O2) have bad readings.
To add to my confusion I believe if the ECM senses that the motor is running too rich in the case of a bad cat, the ECM will lean out the air/fuel ratio which would also adjust the readings of the O2 sensors. That seems to me to make it even harder to tell whether an O2 sensor or cat is bad when the O2 sensors could be self-adjusting for a bad cat.
According to the article, an O2 sensor needs to respond quickly enough with a voltage jump during a throttle snap. Based on that, the data I collected would lead me to believe sensor 1, bank 2 could be bad since it doesn't show a voltage change from zero for a much longer time than the rest.
Furthermore, my vehicle gets the same MPG it has always gotten and doesn't run poorly or idle roughly. I probably won't be able to help anymore as I've sold my Pathfinder. Good riddance Nissan!