mzdfc3s

iTrader: (2)

P2A03....the most frequent word used in my diction here of late. I will try to give you the background to keep it short. About 15k miles ago P2A03 CEL came on which is Bank 2 Sensor 1 out of performance/out of range. My immediate thought was replace it, so I did...came back on 50 miles later. After that I left it alone for several thousand miles bc I was too worried about it, performance wasn't terribly different. Over time there was a significantly more pronounced "fat" spot throughout the RPM range and you could tell the ECU was dumping fuel.

About 8 weeks ago I finally decided to have VSC done on the slave bc it too was finally feeling like a sloppy cow. Before I took it in I was looking over my warranty and found that I bought the gold preferred package. And with that there is apparently a host of things covered in there that I didn't think normally were. So I had them service the CEL, serpentine, hub bearing, and slave.

All they did for the CEL was replace the 02 and MAF sensors, the MAF was a new code that generated sometime after the first P2A03. Got the car back and it felt a lot different but the CEL came back 80 miles later. Went back in...this time they replace the ECU. Got it back CEL came on 165 miles later. Went back in...this time they're startin to scratch their nutz so they replace the REAR bank 2 sensor 2 02 unit WTF. I let him tell me some crazy reason knowing it would be back in another few days....it did. All the while mind you, when I first dropped it off I suggested you check the exhaust manifold for cracks or test the injectors. Of course Im an idiot for suggesting......

So after the car sits for another week they finally get permission from Mother Nissan to test the injectors. TaDA they finally determine that injector 2 and 4 tested high resistance and replace them. Sounds great, car feels close to right but just not quite.....I still smell a hint of raw fuel and it still "burps" on slight acc/decel.

In between one of the times it was at the shop I got a datalogger to see what was really going on for myself. The comparison of instantaneous fuel trim from bank 1 to bank 2 was different on average by about 15% and the 02 voltage on bank 1 was close to stoich at around .455v compared to the bank 2 side which was coming around .875v. These two voltages would stay consistently that far apart in range throughout various driving conditions. After I got the car back a couple days ago, this time with the sure fix from from Nissan, I logged some more data.

The fuel trim comparisons are a lot closer to what they should be. Bank 2 is only correcting 3-7% different than bank 1 which is closer to 1% correction. However when I said I could still smell the richness I confirmed the presence in the 02 voltages. Bank 2 is still rich at .875v and bank 1 is still stoich at .455v ??????? Now what else could that mean? Maybe the injectors went out early bc they were over correcting for so long trying to get the fuel where it should be that they wore out, all the long there is a different underlying symptom?? I don't know. But Im pretty sure the 02 reading on bank 1 and 2 should be much closer to similar correct?

sorry this got so long, thanks for reading!

onagao

I'm subscribing to this thread.

I wish I had an answer/solution, but I don't. In fact, I'm experiencing a very, very similar problem that I detailed in this thread.

Mine is different in that it's Bank 1 Sensor 1, and the code that comes back is the sister code to yours - P2A00. I really hope you find a solution to this. The only thing that resembles a fix for me is resetting the Learned Fuel Settings within Cipher, which normalizes the over-correction that's occurring between the banks temporarily until it spirals out of control again. I don't understand this, and your title is entirely appropriate; it truly is a gremlin from Hell. Question, though. Have you experienced any noticeable drop in power?

Somebody please help with this.

mzdfc3s

iTrader: (2)

drop in power was more significant before the MAF was replaced and the car was running in total limp mode. after that it got better but there was still a noticeable "stumble" in the WOT rpm range. Now that the injectors were replaced it is closer to feeling normal, but my suspicion is that there is still something causing an over corrective rich condition on bank 2 only. This i relate to the unburnt fuel smell, burping exhaust, and the high 02 reading....

rcdash

iTrader: (18)

Did you work through the FSM service procedure for that code? I'd look it up myself but that code doesn't exist for my model year.

onagao

I think I read somewhere that both the P2A00 and P2A03 codes were for 06+ models.

dkhanijao

iTrader: (4)

I have the same code. Still can't figure it out what's causing the problem.

rcdash

iTrader: (18)

Well if you haven't read the FSM yet, I don't know what to tell you. It's a free download if you put a little effort into looking for it, or max $20 download from Nissan.

mzdfc3s

iTrader: (2)

everything in the FSM has been looked at by myself and everything Nissan has done is in accordance with the FSM. My very last possible conclusion is a cracked exhaust manifold drawing in free air which would in turn fool the ecu into thinking there is a lean condition forcing itself to over0correct rich. The only thing the dealership says is they can't hear a leak and have not taken the time to remove the manifold to examine closely. I would imagine though that this is the next step if this CEL comes back. Maybe I am missing something or dont understand correctly...am I correct to assume that both banks front 02 reading should be nearly the same? I really can't imagine a constant condition that would always show one bank significantly higher than the other??

turbotoy

iTrader: (17)

The banks run different AFR due to manifold design. The twin intakes was supposed to help with this problem on the later model VQ. This could still be an issue though causing bank to bank differences.
I have had the p2ao3 code off and on. I replaced O2 sensors and now I get it on both banks. p2ao3 and p2aoo. I am going to check the injectors after reading this because I have checked everything else

onagao

Definitely post back here if you find out. It would be great to finally figure out what is causing this problem, because I get the impression that it's happening to a small number of us, but nobody has any idea why.

Also, the banks naturally tend run different AFRs, but that's when they're not correcting. It's when they start over-correcting and creating the discrepancy in the first place that we have this stupid problem.

mzdfc3s

iTrader: (2)

I have read this before and if this is truly a design condition than it should show in one bank only, I would think. Back to the AFRs, I unfortunately do not have Cypher and my datalogger only pulls o2 voltages. this should still be some relatively accurate information for determining which bank is running stoich or rich. We know that voltages around the .450v is considered stoich and close to the target 14.7 AFR. While a voltage higher >.450v is considered rich and lower <.450v is considered to be lean basic assumption can be made. I don't know if someone has figured out an equation or log for converting the voltage to AFR value but at least in my case, bank 1 runs about .450v bank 2 runs about .875v, i think the actual AFRs are quite a bit different and outside any design parameters regardless of intake design. I could be worng....

I forgot to mention in my first post, on a side note. My car has literally been to Nissan 6 times in the last 8 weeks. Average length of stay is 4 days each time. I havent lost my cool with them yet bc I know its perplexing. Also in the middle of all this my warranty expired, approximately 4 weeks ago. I was worried about having to fight with them but they continue to do work under warranty due to the fact I was in there before my warranty expired, so thats pretty cool on their part! Ive roughly tallied the work they have done so far to about 3K!

turbotoy

iTrader: (17)

I hear what you are saying and you are correct.

onagao

Swapped O2 sensors today and did a full test per the FSM. The test checked out fine, and the over-correction did not swap sides with the suspect O2 sensor. The same bank is doing the same thing as before. So it's not the O2 sensor... and now I've got nothing

mzdfc3s

iTrader: (2)

so the only difference between us is different banks....do you have access to your furl trims and o2 readings on each side by chance?

onagao

That's what it looks like. Check the thread I linked earlier and let me know if that data is what you're asking for. If not, I have various datalogs on my computer that I can post up if you want me to.

mzdfc3s

iTrader: (2)

Yes sir I did check that out and I remember coming across it a couple weeks ago. I can't tell by looking at your log if the two columns to rows from the end are supposed to be raw o2 voltages or not. the numbers look like they could be possible but they shouldnt be that high when idling so I dont know. Your fuel trims look close to what my ECU is throwing with the exception of WOT. You go right back to 0% correction and I carry the same 10%+ difference through the entire range? Since I dont have cypher I cant be sure what the afr values are. See if you can find out o2 voltages and we'll be looking at the same stuff......or you could send me your unit and Ill check mine Essentially though, I believe the only thing the cypher does is convert those o2 voltages to an AFR value via logarithmic function. If someone can find that equation Id be set too

onagao

Those should be the wideband sensor voltage outputs.... I'll grab some other datalogs and look at the readouts. It's possible we're reading two different things, though.

Also, what mods do you have on your car (beyond the ones listed in your sig)? I'm curious to see any similarities between our setups. I know one of the other guys who mentioned above happens to have an 06 and almost the same setup as mine.... I'm wondering if a particular combination of mods is causing the anomaly.

mzdfc3s

iTrader: (2)

nope just whats listed plus kn drop ins

onagao

Well, I was shown an interesting tidbit in the FSM that suggests that under certain circumstances, the rear O2 sensors (sensor 2) can control the correction of the AFR. Now it doesn't say what conditions or circumstances those are - just that under most normal conditions, it doesn't control it. This was news to me, as I had thought it was only the upstream sensors that controlled anything and the downstream sensors were for catalytic efficiency purposes only.

If anyone knows and could chime in regarding how/when/why the rear O2 sensors would control anything, that would be great.

To eliminate variables and narrow down our search, Chris swapped the two rear sensors. We hope this will flip the problem. As it is, the problem went away for the 20 minutes we were out and about testing it. I'm definitely not going to say it's fixed, but I'll have more on this once I figure out what - if anything - it did to the problem. I'm hoping it might be a solution.

mzdfc3s

iTrader: (2)

I did not know that about the rear o2 sensors...but that would explain why one of the several things Nissan has tried was to replace the rear o2 as well. To no avail tho it did nothing.

Anyway......UPDATE

The gremlin has returned. CEL P2A03 came back on this morning so apparently the bad injectors likely contributed to this problem but did not in fact cause it The dealership didnt get back to me today when I called them. They wanted to talk with Mother Nissan before I brought it in and Im guessing they had the day off today. We shall see, the saga continues. If nothing else I will see this to the end so we can have some answers. It is getting to be quite a pain in the *** to drop off and pick up tho......happy easter