bjr

What is considered normal for a stock 05 engine? My issue is that O2B1S1 reads only about half of O2B2S1. (0.3 vs. 0.6). This is at any steady state (idle, cruising steady at 40mph, cruising steady at 80mph). My fuel trims are showing changing + or - single digit trims around 0 fairly normal on both banks and pretty equal. Both S1 sensors test normal Ohm range per FSM. Both seem to react quickly on the OBDii scanner to throttle blips. At first I thought B1 seemed a little lean but now I am more focused on B2 because with a quick throttle blip it can read 1.27 briefly and in theory should read only 0.1 to 0.9. I don't suspect any of the 4 sensors to be faulty yet because they all react to throttle changes, and pass FSM tests but I have NO IDEA now what I should be looking for if one bank is different than the other - what is that a symptom of? It seems like on other cars that they should be equal from my research. Also my downstream o2s are equal. Always about 0.7 at steady state idle or cruise/steady throttle for B1S2 and B2S2.
I am at what I hope is the end stages of tracking and fixing a misfire problem but I have to wait and see if my fixes dealt with that. It was so intermittent that it doesn't happen but once a week sometimes. So I have checked a lot of other things that passed in the last few weeks but am stumped about the o2 readings since I never studied live readings before this misfire came up. I am not sure if the live data conflict with the O2s are related or not to the misfire. At first I was sure it did, now I'm starting to separate the two "problems" Need to know what is "normal" on this engine???
I have 4 pages of notes from the misfire ordeal and some live readings out on the highway saved. Just don't want to overwhelm info at this point if someone can tell me yes/no on "normal" and what to look for if this is not normal. Can post much more later...

iStan

iTrader: (29)

B1S1 ~ .3
B1S2 ~ .3

B2S1 ~ .6
B2S2 ~ .3
Is that about right?

I am having a similar problem. I am throwing code P2A00 (B1S1 Circuit Range/Perf). My readings are similar, expect my B2S2 is reading closer to the B2S1 reading (ie B2S2 ~.6).

Have you tried switching the sensors on the banks? That should pinpoint if it is a bank issue or a sensor issue. I'm curious to see what you find.

bjr

ugh. Well, yes and no. I just pulled my notes out of the garage and it turns out that I remembered the S2 sensors closely matching the wrong S1 sensor. They are both usually around 0.7 (fixed that above in post 1)

So mine would go approximately
B1S1 ~ .3
B1S2 ~ .7

B2S1 ~ .6
B2S2 ~ .7

But yes, same imbalance for the bank and similar numbers as yours. But your S2 sensors are lean compared to mine.
I wonder if the P2A00 uses the S2 readings to conclude anything since I am not getting that code and my B1S1 is as low as yours. I'll have to look up P2A00 in the FSM and see what it's all about.
Even though the sensors would be difficult to remove (rust!) I did think about what you said and since Autozone listed the Pre-cat sensors as being Passenger and Driver side specific I figured it would be a waste of time to look into swapping my S1 sensors. Maybe I'll confirm that tomorrow because I don't remember a reason that they would physically be shaped different or whatever could be specific. Both of the connectors are the same and they both thread into the manifolds. hmmm Thanks for the feedback, give me a little time to check it out...

Oh, if your S2 readings are lean are your STFT numbers negative most of the time?


Here is one example of my live data

Live Data Trigger Frame +1
PID Unit Frame
Fuel System 1 Status CL
Fuel System 2 Status CL
Calculated LOAD Value % 45.49
Engine Coolant Temp *F 183.20
Short Term Fuel Trim-Bank 1 % 0.00
Long Term Fuel Trim-Bank 1 % 5.47
Short Term Fuel Trim-Bank 2 % 0.00
Long Term Fuel Trim-Bank 2 % 6.25
Engine RPM 3100.00
Vehicle Speed Sensor mph 73.75
Ignition Timing Advance #1 Cylinder deg 34.00
Intake Air Temperature *F 24.80
Air Flow Rate from Mass Air Flow Sensor lb/min 5.37
Absolute Throttle Position % 11.37
Bank 1 - Sensor 1 V 0.29
Bank 1 - Sensor 1 % 0.78
Bank 1 - Sensor 2 V 0.76
Bank 2 - Sensor 1 V 0.59
Bank 2 - Sensor 1 % -0.78
Bank 2 - Sensor 2 V 0.74
OBD Requirements OBD2
Distance Traveled while MIL ON miles 0.00

iStan

iTrader: (29)

I do not recall it being driver/passenger specific. I do have an auto 06, so it is the same motor, and I thought the 05 have A/F sensors precat. I believe Nissan stores use the same part number for both, but that may be another way to confirm. The only reason I can think of for different sensors is wire length, which very well could be the case.

Not for sure, but I believe any of my readings on fueltrim would not help because of the Vortech. I can grab the data for you.

I'll also go datalog a g35 and see what king of readings I get from it.

I would have thought your readings would be more indicative of a bad B1S1. How far have you driven since you started the logs?

With my readings, if the sensor was bad, I would have expected a situation where B1S2 would be greatly different from B1S1 (like yours) but that is not the case. So, within the next week or so, I plan on changing the cat with new gaskets (exhaust leak seems to be one of the causes for my code) and seeing if I throw a different code or if everything stays the same.

myfirstzcar

Fuel trims are good, no cel, what's the problem?

bjr

myfirstzcar - Not sure. Just don't want to let something go that does not seem right and long term destroy something being lean. I searched a lot of other sites for info and every v6 and v8 I can find looked like both banks should match. When it got down to one of my last symptoms I was hoping that a lean reading on that side might be from a stuck EVAP purge solenoid but it is working good.

I understand that it may be impossible for them to be equal since both banks have to share the same air source then add the right amount of fuel but still seems like I could have a small problem. Just looking for someone to say it's normal so I can stop looking at it all together? *You are right, if I hadn't got codes for misfire I would have been driving it no problem. Also don't know how many years(?) the O2 readings have been this way. I drive it 80 miles every day so I am not paranoid but am still looking at it...

bjr

05 is A/F pre-cat. I'm sure Autozone could be wrong

I would be interested to see the g35, is it stock?

This has been going on for about 7 weeks, which would be over 3,000 miles for me. I was slowly working on a random misfire (P0300) and noticed the O2 readings the second week but I am betting they have been that way much much longer from what I am figuring out so far.

Exhaust is a good idea. Misfire codes tell you to check the cat for dents, obstructions. A leak makes more sense if this is a separate problem that has to get worse to get a code. I should at least crawl under there and put some PB blaster on the O2 threads in case I want to swap them or take them out and also check for holes. I know my cats lost their outside shields in the last year but thought they were ok. Probably time to take another look.

bjr

looks like Nissan site shows pre-cat the same and after cat side specific and the wires go a different direction. Maybe I will be doing a swap for diagnostics. But it will be awhile until the rust breaks up so I don't snap them off. Looking forward to any other advice in the meantime...

iStan

iTrader: (29)

That sounds about right with the sensors. The G35 is not stock, all intake and exhaust mods, but it should still be good to see relative numbers on it. Should be able to do that very shortly.

cudaben

I have done bunches of expensive and extensive advanced automotive classes specializing in electrical. it has been about a year since i took my last one so i may be rusty. gimme some time with this and lets chat it'll come back to me.

lets try the simple FREE things first.

switch the sensors side to side and see if the voltage follows the sensor. if it does chances are your sensor is funk... if it does not follow then you need to start looking into possible causes for a rich (low oxygen) issue.


to my knowledge any and all o2 sensors after the cat are ONLY there to monitor cat efficiency.

myfirstzcar

.3 is slightly lean and .6 is pretty good. Which side is reading .3?

bjr

myfirstzcar - The 0.3 is on passenger side before cat, B1S1.


I did not get a chance to swap pre-cat sensors side to side. Looks like a weekend project to me. Will the sensors be as rusted in as a suspension or chassis bolt(for example) on a high mileage summer/winter driven car or are the threads protected from the elements as much as they appear? There is a wide temperature range of heat cycling on the threads though even if rust is minimal. Should I expect a test of patience to get them out with penetrating oil or will they come out relatively easy? How easy can they break off?

I was looking for a few tips on why the readings are different or even if I should be worried about it before having to do this but this swap may be the only way to further diagnose if it's the sensor or something else causing the reading. There is no good test for the sensors I can find. They both already pass the FSM specs. for Ohm reading and no shorts. I take it that everyone else feels the two S1 sensors should read equal numbers? Hope to still verify that with someone.


I believe everyone about lower reading is rich but in all my readings, higher is richer and lower is leaner (talking about 0 to 1 scale most scanners display no matter if it is O2 or A/F sensor). Why am I confused about this? I must have missed something.

cudaben

There are a ton of possible reasons it could be lean... but lets not even go there until u know for sure that you have an issue.

Get some good penetrating oil, spray the bung, buy a actual O2 sensor socket and be patient. remember if you are backing it out and it stops -really stuck- try tightening it some then loosening it again, back and forth until it comes out.

myfirstzcar

The lower the volts, the leaner the mix.

bjr

Got it. Treat it like a spark plug and expect the worst!

adrift_foolish1

Your fuel trims look good. I would test the sensors by creating a vacuum leak, watching stft go positive. Plug it up and spray some propane in the intake, watch the fuel trims go negative. If they both respond I would think about running down a different rabbit hole.

bjr

Sorry for being away so long. After coming off some boring vacation days at home and trying to go back to work for two days I got the flu Friday and we also had about 24" of snow in the last 10 days or so. I've just been sleeping and snowblowing. Todays high is -8degF! It's 25 in my garage. I have a small furnace but it's just not worth it right now since the car runs reliably. If it was summer we would have all figured it out and fixed it by now. Perfect Z weather, huh? For SOME reason I just haven't had much motivation to put the car up on stands high enough to work on it

My next step was going to be swapping S1 sensors side to side just to positively identify the problem stays with the bank and the sensors are OK.

related to what adrift_foolish1 just brings up I feel like all 4 of the sensors are responding the same speed (reaction time) and full range when trying to work them a little. Like WOT to abrupt lift while driving, quick throttle blips in the garage, etc.
When I was focused on chasing mifire, I did pull the cap on the front vacuum nipple on the intake manifold. Instantly both banks stft pegged at +25 (maybe the max the injectors can do?) and tried to watch all 4 O2 sensors but the ECU reacts so much quicker than the scan tool (my guess) is that the readings just didn't change much at all. I think all of the o2 went just a little higher (towards 1) but it was in the second decimal place. I ended up using the throttle playing I just mentioned above to end up getting an idea of if the o2 sensors seemed to be able to read between 0.1 and 0.9 like they should. Didn't have any propane handy to go rich.

So it will be at least a week or two on a Sunday before I get to this but I have some good tips what to do next. If I can confirm all 4 sensors are working correctly it sounds like you all are saying that bank1 with the 0.3 is a little lean? Bank 2 with 0.6 is about right or slightly rich right? So if I have already done everyting in my ability to confirm ignition is OK from all my misfire diagnosis, and I can determine that the o2 sensors are OK, and I have already done a home-made smoke test for vacuum leaks and bought a vacuum gauge both indicating to me that I don't have vacuum leaks - the next guess might be a partially blocked fuel injector on bank1?

IF SO, can those be effectively cleaned on the car by the dealer temporarily or is the only option remove to ultasonic clean and bench test (and at this age check all 6)? This is my DD and only ride to work and can't easily be down for days while injectors are in the mail.

myfirstzcar

I would suggest going to a reputable shop that has some kind of proper fuel injection machine.....A shop that will actually do the work and not just say they did it.

adrift_foolish1

Theres a lot of things that could cause o2 between banks to be different. Exhaust leaks, plugged cats, bad o2. If you are comfortable that the o2's are reading their full range they're probably ok.

The computer should be making trim corrections in closed loop if the o2's are out. If its not and you don't have a cel, fuel trims are near zero; maybe double check with a different scan tool? Also, did you check long term and short term fuel trim?

bjr

I had some time today to swap the S1 sensors. I had no problems at all but it's time consuming. I put PB blaster on them every night when I got home and the car had cooled a little so I didn't burn myself and the sensors came right out like they were brand new. I think it took me 3 or 4 hours but I had to start by sweeping up all of the snow/melted snow off the garage floor mat And it always takes me 30-45 minutes to comforably/carefully get the car on 4 jack stands before I risk climbing under there

For a quick update absolutely nothing seems to have changed. I still get
b1s1 0.3
b1s2 0.7
b2s1 0.6
b2s2 0.7
this is at a very steady 40mph when all readings settle down like before.
Both sides STFT are bouncing between -3 and +3 which is pretty good.

I will post pics next and keep them in a separate response since I had to sign up for a new image host I'm not familiar with yet.

I am guessing that I should have started the car with it on stands and either with both sensors out or one out checked for vacuum or pressure at the bung to determine cat plugged or not. Didn't know how long I could run it like that so I just skipped it to call it a successful day. But I can still check that with an IR temperature gun one night when I get home and the car is as hot as it gets and running to check in and out temps. I would think if it was plugged enough to get such different readings on o2 that it would reveal itself in another way too like sputtering on accelleration.

I think that the next easy thing for me to do since I built myself a smoke machine for diagnosing my earlier misfire is to plug one muffler tip, put smoke in the other then look for leaks. If there are small leaks at flanges or something put duct tape over them temporarily since the car will be cold and keep going until I reach the exhaust manifold.

You guys also mentioned partially blocked fuel injector. Wouldn't that show some different readings on the scan tool whether it was idle, WOT, in gear, in neutral (i.e. different loads)?

Is there also any other ways you can think to use my scan tool and a passenger to watch anything else. I'm picking up on how the o2 sensors and fuel trims react to WOT and heavy decel. after that (heavy engine braking in gear basically) and am starting to wonder if there are any more creative ways to track this down with the scan tool.

*****Also, at this point is it a waste of time until it gets worse? There are no codes. Am I risking anything with them reading that different? (0.3 one side 0.6 on the other)