I too would usually assume a bad o2 sensor, but in this case, it reports back perfectly under WOT, and under most closed loop conditions.

Hmmm... the ECU wideband driver could be toast. I cannot find a PA200 code in my FSM (for my 2004.5 G35 coupe).

Sorry for the typo. The code was P2A00, not "PA200" as I had originally written.

Just an update:
The problem is persisting, and the car threw another P2A00 code last night. The car was back to idling with Bank 1 running ~1.5 AFR richer. I decided to "Reset Learned Fuel Settings" within Cipher, and everything instantly went back to normal.

I'm getting my oil changed tomorrow morning, and unless that magically fixes the problem, I'm going to bite the bullet and buy a new O2 sensor for Bank 1.

Question 1: Any ideas as to the cause of this that don't involve a bad O2 sensor?

Question 2: Bosch or OEM?


I wish the Bank1One that held money would start over-correcting and making me run rich. That's a problem I wouldn't mind having.

Today, Chris (Failsafe Performance) went through and did a hardcore check of all the questionable systems associated with a P2A00 error code per the FSM. Everything checked out fine, and we ended up deciding to swap the O2 sensors in the hope that the issue would switch banks and thus confirm it was a bad sensor.

However, it did not. Bank 1 continues to over-correct just as before, and I now know that it was not a bad O2 sensor after all. I also now have absolutely no idea what is causing this problem.

FML

I'm bumping this old thread because while everyone's interest seems dead, my problem is still alive and kicking my ass. There are at least a dozen threads scattered around here where people have the P2A00 or P2A03 sister codes, but none of them come to any conclusions. Either people solve these problems and never report back, or they just keep on going with the codes/issues plaguing them.

Could somebody PLEASE chime in with some wisdom and point me in the right direction. I don't want to spend another dime on my car before this issue is solved.

Did you try unplugging the intake cams?

I can't see any physical condition that would cause the ECU to add fuel when running rich unless there was a bug in the ROM or Cipher itself. Good luck with this one...

clogged exhaust?
 

Verify that your WB sensors are not crossed (B1 sensor on B2 connector), and also verify that your exhaust is not getting intermittently clogged on one side (steel wool inside ART pipes?)

Ever since buying Cipher, I have been monitoring B2 sometimes going leaner than B1 by ~0.25 rate. Long ago I swapped O2 sensors – no change. However few months ago I started seeing much worse differences and yet, like you, B1 being overcorrected at the same time:
Then suddenly one day, the opposite, B1 being leaner than B2, by lot - but not always:
I was suggested to replace injectors. Which I did – no change.
Then I run into article about P0300 which I was getting at that time. BTW my 04 manual also does not have those P2A// codes that you are getting.

Gutted out cats solved my issue = back to normal (B2 being leaner than B1 by ~0.25 rate).

I hope this will help you. Good luck.

I haven't tried that one yet. I'll do some looking into that, but I may end up needing to get with you regarding what to look for and what to expect when I do. It sounds fairly straightforward, though.

I would tend to agree. But someone else on here has had a similar unsolved problem and even went so far as to replace the ECU altogether, but the problem has continued. Combine that with the fact that I've seen this on three separate computers and two separate cables, with and without the tune, and it doesn't sound electronic.

:dunno:

Thanks for the link. I'm going to give that a good read and hopefully find something useful in it. I might have to take off the ART Pipes and give them a once-over to make sure nothing crazy is going on with them. I'll probably hop back on and post if something in the linked article catches my eye.

This may or may not be relative, however, its something one might consider... The fuel feed line feeds into the passenger side(B1) fuel rail before entering the drivers side (B2). So naturally the passenger side will be a smidge richer than the drivers side. It might be .2-.5 richer, like I said may not be much. But with a slowly failing O2 sensor, it might make things worse they
appear. Have you replaced the sensor yet? And you have swapped o2s already correct? Is everythin else practically the same such as intake cam phasing %s(this may not make a difference) , or injector pulse widths?

Well, we've swapped the O2 sensors, and the problem stayed on the same side, so that eliminates the possibility of it being a bad O2 sensor. And even still, the fact that that it's reading rich (correctly) and still adding fuel is what makes it so strange.

Everything isn't necessarily the same; the intake cam readings are significantly off when the problem is rearing its ugly head. Running theory is that it's a byproduct of the car trying to add more fuel. I went down to Failsafe, and we unplugged the intake cam sensors to see if that would have anything to do with it, and at first it looked like the problem went away, but instead it came right back like before.

Injector pulse widths... not sure if we checked those. I'll have to double-check and get back. I feel like Cipher doesn't provide that option, but I could be wrong.

NEW DEVELOPMENT:
As far as new developments go, while Chris was being awesome and helping me in my quest to figure this crap out, we narrowed down what appears to be a condition under which the AFR imbalance comes back up. At idle, the AFRs are supposed to be steady around 14.7 or thereabouts. If I get on the gas and rev it up to somewhere high and slowly bring it back down, it stays normal. However, if I let off suddenly and trigger the fuel cutoff, it triggers the AFR imbalance issue that's been plaguing me. Bank 1 will drop down to around 13.2 while Bank 2 stays at 14.7'sh and they just hover there for anywhere from 30 seconds to over a minute before suddenly jumping back to 14.7 for both. It's strange.

So I now know of one way that definitely triggers it, and that the condition will disappear over time at random if left alone at idle... only to come back later if triggered again.

So does that mean it's fuel system related? I've cleaned the injectors thoroughly, we've checked the voltages on all of them. I'm thinking about swapping the injectors from one side to the other this week and seeing if that affects anything. I have a feeling, however, that it won't. Any ideas???

I was thinking to try swapping the injectors. At least switch sides to be sure to rule them out.

Yeah... that's the plan for now. I'm really getting tired of spending money on this car and having nothing to show for it. That gets old really fast. :icon22:

it almost sound like a stuck injector... although it wouldn't explain the backwards correction. good luck.

Yeah, I wouldn't think it would explain the overcorrection, either. However, if the "correction factor" that is being put out on Cipher is simply a reading of what is happening instead of what the ECU is trying to make happen, that would open up the door to the possibilty of a mechanical problem like sticking or what not. I guess I'll find out the hard way :dunno:

Just for the sake of not having to reread the whole thread, have you verified there is absolutely no exhaust leaks at or before the last o2 sensor? I've heard that manifold/cat/sensor bung leaks, even those that aren't obvious, will cause this.

since i went turbo i've changed nothing but hte turbo and i'm having this issue but mine is ONLY when i'm building boost.

press the gas, bank 1 goes about 1 point lean until i'm up at full boost then it drops back down to meet the other sensor. I've swapped sensors and the problem always remains on bank 1 (passenger). It's rock solid everywhere else and when under full boost all the way to redline.

I got for a tune at injected next wekend but this problem has been driving me nuts. They were within .1 a/f of them before on my vortech so i know the ecu and widebands are ok. I hope hal can get it settled out. If i pull bank 1 down to be the proper a/f in those areas then bank 2 is super rich and i don't want that either.

^ why not just pull down bank1 injector trims? that way bank 2 doesnt change.