This link explains how O2's work. I know it's a chevy link, but it's all the same.

Understanding Oxygen Sensors to Diagnose Fault Codes

 

I don't have any fault codes for sensors or otherwise and the voltage constantly switched @ all 4 sensors, it has always been like that but this D2 is the only vehicle that I have seriously investigated on a regular basis.

 

if your post cat 02's are mimicking the pre cat 02's, your catalytic converters are toast.

 

damn that's crazy. how will I know when the cat' converters are faulty enough to warrant a replacement?? the truck runs good and no CEL

--never any problems with emissions testing/registration. so I'm sure they will let me know as the truck won't pass emission if the cat's aren't collecting the hazardous stuff, right?

 

If no light on the dash and if the DEQ doesn't do a sniff test on your exhaust I guess your fine? Idk

 

I agree with this. Remember the post-cat sensors have nothing to do with engine management. A post-cat O2 code simply indicates to you, and to your DEQ, that you need a new cat.

I disagree that the post-cat O2s should always read a steady voltage. Perhaps when new but not in my 17-year old truck.

Several weeks ago I accidentally set up my UltraGauge to read Bank 2 Sensor 2 instead of B2S1. What I observed is that the B2S2 voltage switched back and forth around 0.45v but it did so much more slowly than the pre-cat sensor. That is what it should do, as I just now confirmed by again digging into the RAVE (page 270 of my RAVE pdf).

 

Rear O2's put out a CONSTANT voltage when the catalytic is combusting the most waste.

Example-
UP a hill with the pedal down you might get .245 volts DC out of the rear O2's.
At idle - 0 volts.

The rear O2's exist to make sure the catalytic converter is working correctly.

See
http://jeffreyfall.com/landrover

 

I've got new cats so I know that isn't my problem. I ordered new walker sensors and after I get them installed, I'll report back. I think a lot of mine was the fact that the front one is bad and causing it to burn lean on bank 2 hence it showing a higher reading on the rear of bank 2

 

Well swapped out my wires and put kingsborne 8mm with the Kevlar boot protectors (yea snake oil I know) went for about a 30 mile test drive and now the o2 sensors seem to be working perfectly and have no codes!!!! I did order a set of walker o2 upstream sensors and still will put them on.

 

Please keep us in the loop.