I find it curious that you originally had a B1 PO420 code with B1 AF Sensor with a 0.3V and a B2 with a 0.6V. While I have a B2 PO430 code with the exact same two AF Sensor Volt readings (B1 0.3V, B2 0.6V)? You could assume the Voltage rates would/should be reversed? But not so!
Just did a propane test, AF and O2 sensors, as well as STFT and LTFT data was collected. Although the B1 and B2 AF Sensors starting baseline voltage is different, during the test the rate of change for both sensors was almost identical, when B1 would go down to 0.25V, B2 would go down to 0.55V, the same 0.05V drop.
While using my scanner @ 1500 RPM no load, no propane I did find a really high switching rate on B2 O2 Sensor compared to B1 O2 Sensor.
Also found FT difference when both LTFT and STFT where added together, B1 was avg around 3% while B2 was avg -12% (rich). The high switch rate highly indicates B2 Cat needs to be R&R. Not sure about the FT?
Also why do I have a high mpg rate?
So is this bad Cat the cause to why the FT on B2 is an avg of -12% and is it also the cause of my high mpg rate, or is the -12% FT the cause of the Cat going bad and is the result of one or more other non-Cat components malfunctioning? Time for more research.
During propane test I noticed both AF Sensors voltage would drop an equal amount for a few seconds then return to the normal individual voltage rates even with propane still on, this suggested to me the ECM, AF and O2 sensors are all operating in good order to keep the engine as close as possible to the 14.7 to 1 ratio. So the ECM cut fuel injector pulse rate during propane injection based on the input data from both of the banks AF and O2 sensors. Both AF Sensor Volts decreased by the same voltage amount before returning back to normal individual rate, this indicates to me that both banks are operating the same, if one of the banks was having misfires due to a bad coil, plug or fuel injector, these voltage drops would be different? Also this would rule out a specific Bank only intake leak or exhaust leak? Am I correct in this analysis? If both AF Sensors closely mirror each others actions (except for our unknown reason for the baseline 0.3V and 0.6V difference) would that not indicate the banks are working the same, and if one bank had a specific problem the AF Sensor voltage fluctuations during RPM changes would be way different even if it was for a very short time until the ECM changed the fuel injection pulse rate on the effected bank?
I can understand the O2 Sensor having way different readings because of a Cat being clogged up, being inefficient compared to the good bank. But the AF Sensors should read the same unless there is a specific problem with one of the AF Sensors or a problem on that specific bank that would/should cause another code (like a misfire code) besides the PO420/PO430 to come on? You would think after this diagnostic and if no other problems are found and no other codes set you could assume it is only the Cat that has gone bad and nothing else?
I did notice a lag on B1 O2 Sensor compared to B2 O2, but it is B2 with the Cat code, so is B1 slow or is B2 reacting faster because the Cat is not working. I believe it is because B2 Cat is not working (like it is not even there, that means it is not currently clogged I assume). Because we have AF sensors we cannot compare a specific banks O2 upstream to an O2 downstream, but we can compare B1 O2 to B2 O2.
I did read when certain codes set it stops the ECM from further self diagnostics until that code is fixed, I believe the case I read about was an AF Sensor code and thus no other emissions self test would be completed by the ECM until that code was no longer detected. That makes sense, because without a functional AF Sensor the ECM would not get the data to know the Cat has also gone bad, but its also why you hear about people feeling they are getting ripped off because they pay to have one code fixed then soon after a new different code pops up that is usually more expensive to fix.
I have done multiple tests to look for intake leaks, by using scanner, water, smoke, propane, but the most reliable test (I believe) was done with a vacuum gauge. You can use a vacuum gauge to test intake, exhaust, valves, rings, head gasket, and improper idle mixture. All tests were good.
I still have my high idle code PO507, in park it idles @ 1500 RPM.
After checking for intake leaks and the PCV the next step is to take it to a shop to have the NSB done with a high end diagnostic machine, if that's a no-go, depending on the data found, maybe next step a TB R&R?
If and when I make to a shop I will check out the AF Sensor Volt readings on the shop's machine tester.
It would be great if we had someone else in the forum with a 05/06 PF and an after market scanner to tell us their AF Sensor readings. If 3 PF's have the the same B1 0.3V and B2 0.6V reading, I would assume that would prove that these are the normal baseline volt rates assigned to the sensors.
So the ECM has no control over the amount of oxygen volume entering the engine to include a specific bank, it only detects the ratio of oxygen to fuel. The ECM does have control over how much fuel will be used through the injectors by adjusting pulse length rate in an attempt to align with the oxygen to keep the ratio of 1 pound of fuel to 14.7 pounds of "oxygen" (or is it air?)
The ECM so far as I have read only reports STFT and LTFT, it does not make any fuel injector pulse rate changes based off these two sets of collected data.
What about the Throttle Body, is the butterfly valve angle degree only based off peddle depression (or cruse control setting), from what I understand this is mostly how it works? In other words the ECM makes no butterfly angle adjustments to attempt to control the 1 to 14.7 ratio. Not sure what happens during limp mode, how does the ECM control the engine components to put it into limp mode to prevent the engine from going above 2500 RPM or above of 2nd gear? I suspect it would be by limiting fuel injector pulses and or preventing the transmission from working above 2nd gear? The ECM makes no fuel injector pulse rate adjustments when a misfire code becomes active due to any component malfunction, the only adjustment it makes is based off the AF and O2 sensors or when it detects a performance issue that will cause it to go into limp mode, I assume that would happen if the 1 to 14.7 ratio goes over a predetermined set limit, and or if the transmission started to fail to the point it might seize up?
So if one or more components are not functioning correctly but have not misbehaved bad enough to set there own code (if there even is a code to be set) that could cause a code like PO430 or PO507 to occur, and now its time to diagnose, or just start changing parts from easy/cheap to hard/expensive, or let the shop fix it.
But I like working on cars, and I plan on keeping my PF for as long as practical, I am going to try to accurately diagnose through research, and getting advice (like this blog). I bought this PF new, and now its starting to have issues that require more knowledge on how to trouble shoot and repair correctly, my biggest road block to this is not having advanced diagnostic equipment and the expertise to use it. I did hear about a do-it-yourself repair place here in Vegas, maybe they have a high end diagnostic with pay as you go tech. I just looked them up, closed now, they have a LAUNCH SCAN PAD, a lot more ability then my $99.00 blue driver. Cool for $50 an hr a tech will help you.
I read on the Nissan forum several ways to possible fix a PO507, so far I have tried them all several times, no-go, still one more to do, one person claimed they fixed PO507 by re-cleaning TB again this time off engine and lubed up butterfly rod, did relearn, I will give it a try. I am so tempted to take TB apart by drilling IAC cover rivets out, I just might do that if it comes down to the only option left is to R&R it, it will be worth the core charge to me to be able to tinker with it in the very remote chance I could repair the IAC guts.
Sorry for the long post, but I mainly write this out to help myself think the problem through, and to get feed back where I am wrong.
Hey good luck with the ECM repair, your info and that of the others along with the many suggestions on this blog has helped me in my decision making on how I should work my code problems.
Thanks everyone for the help, will update.
I look forward to reading the cure that resolved your code, its like a detective story with many plot twists, a surprise ending is coming.