[FIXED] Nissan Murano 2015 3.5L P2096 Post Catalyst Fuel Trim

Nissan Murano 2015 3.5L P2096 Post Catalyst Fuel Trim

Code can be set at low speeds below 25mph under light load. Is usually a Past code.

Nissan Techline is sending me on wild goose chases and having me throw parts at the problem. The latest thing is saying the exhaust has a crack in it and is leaking as the engine rocks at low speeds. They require us to have a fancy smoke machine that can do turbo piping leak testing. I had 5psi in that exhaust and NO leaks. I'm not buying there story.

They also suggested I might be having a cat clog and its forcing more air down the other bank. Even though I have no driveability issues or any other codes.....I'm calling B.S.

NO driveabilty issues just the light.

Using the Consult 3+ during a active fuel test. The A/F's and 02's all respond equally and quickly to commanded fuel delivery changes. So I do not suspect a sensor issue. Bank 1 is adding more fuel than bank 2 during normal operation. A/F might be around 110 compared to 104 or so. It varies. The freeze frame data would suggest their is NO issues looking at that data.

Nissan has a PID called A/F ADJ 1 and A/F ADJ 2. I'm guessing that this represents the adjustments made by the ECM as part of the self learning. When you clear the self learn, its all and well. It takes a while of driving the car like many many miles for it to do back to the skewed readings I have been finding looking at data once the codes have set. Not uncommon to see something like this. A/F ADJ 1 = .785. A/F ADJ 2 =.080. Nissan does not tell you jack crap on a LOT of things which makes diagnosis even worse.

Their pinpoint tests are complete crap. I cannot tell you the last time I used one.

This is not my first go around with these vehicles and this code. Its very common at this point. I don't think it is sensor or leaks or anything else. IMHO, its a programming issue. They don't want to admit that or even acknowledge my suggestion. I feel they are grasping at straws.
If these vehicles are wound up so tight on tolerance for programming and they are having issues this young, they will never be old cars, they will go to the junk yard very fast.

Any ideas?

The geniuses at techline cannot fit it either. I'm not sure I don't know more than they do on any given day.

Hey 93Rubie! I believe you when you say there are no exhaust leaks. I've got my own pressurized exhaust tester, and it's done wonders for me with finding exhaust leaks. I also don't buy the partially clogged cat theory. I think you'd see a difference in A/F ratio sensors at WOT if that were true.

This is a bit out there, but is there any possibility of a injector issue? I ask because GM techs have been chasing post catalyst codes on their vehicles for years now, and it often comes down to clogged injectors. Not enough to cause a running issue, but enough to piss off the post cat monitor. Just thinking out loud, mostly.

For our info, what other parts have they had you throw at it so far?

Parts changed. Both post cat 02's done by another tech before I was involved.
I replaced the Bank 1 A/F per Nissan Techline the last time.

I talked to them today and actually got a guy that seemed to actually know a thing or two. Seems like its hit or miss with them. Half the time I know more than they do and I DON'T have access to their internal data base of engineering and such.

Long story short we tired a different approach to replicating the code. We warmed up the vehicle at idle and did the active fuel tests that way. I had been replicating FF data and had driven it and fully warmed up before I did the active fuel test. We found BOTH rear 02's are NOT reading correctly. A/F's are ok. When I had driven it they got hotter and worked better without a hitch. Cool (so to speak) they act up. FF was misleading in this case.

He also told me their was an internal engineering bulletin around the time of the previous 02 replacements that they had been manufactured incorrectly and thus failing. Thus the vehicle got faulty 02's when built and the replacements.

Crap OEM parts, innovation that excites!
I asked why no TSB, he had no answer for that one.

You guys just wait till the newest stuff becomes a few years old or so. The tolerances on OBD emissions is VERY tight. Even small pin hole leaks will be popping codes unlike older vehicles. So in the rust belt here in PA, that means shelling out money for GOOD replacement exhausts early and NOT the aftermarket walker and stuff that fits and seals like crap. Innovation that excites!

93Rubie wrote: Long story short we tired a different approach to replicating the code. We warmed up the vehicle at idle and did the active fuel tests that way. I had been replicating FF data and had driven it and fully warmed up before I did the active fuel test. We found BOTH rear 02's are NOT reading correctly. A/F's are ok. When I had driven it they got hotter and worked better without a hitch. Cool (so to speak) they act up. FF was misleading in this case.

This is the scan tool function that adjusts fuel trim in 1% increments? Sorry, I don't have a Consult 3+, just a Snap-On. Could be way off here. :silly:

How exactly did they not behave correctly? Slow response?

He also told me their was an internal engineering bulletin around the time of the previous 02 replacements that they had been manufactured incorrectly and thus failing. Thus the vehicle got faulty 02's when built and the replacements.

Crap OEM parts, innovation that excites!
I asked why no TSB, he had no answer for that one.

Sounds like you won the tech line lottery! :lol: So you swapped the downstream sensors again?

You guys just wait till the newest stuff becomes a few years old or so. The tolerances on OBD emissions is VERY tight. Even small pin hole leaks will be popping codes unlike older vehicles. So in the rust belt here in PA, that means shelling out money for GOOD replacement exhausts early and NOT the aftermarket walker and stuff that fits and seals like crap. Innovation that excites!

Ah yeah, we're already getting some of that from local customers coming out of warranty. Ford has similar issues with their downstream sensors flagging post cat issues - the sensors have been revised at least once. Then there's GM's and their stupid Fuel Trim Cylinder Balance codes. :silly:

Genuine thanks to you for posting this issue here. Stuff like this ends up helping independent guys like me down the road.

Active Fuel test will change in 1% and 5% increments.

The rear 02's did not respond properly. Full rich 25% for example bank 1 sensor was reading around .54V.

Yes, I swapped sensors today and retested. Same results as before.

I did not get it to set a P2096 code to set on a test drive however. I sent the data to Techline. I don't think anything was fixed.

You should note with these sensors they read Bank 1 around .30V cold and Bank 2 1.78V. They have to warm up for a bit even with a hot engine start, to start working at all.

A/F's are working as expected.

93Rubie wrote: You should note with these sensors they read Bank 1 around .30V cold and Bank 2 1.78V. They have to warm up for a bit even with a hot engine start, to start working at all.

Wait, what? :blink: The .3V on Bank 1 sounds normal to me for a Nissan, but where's the 1.78V coming from on Bank 2? Or, is Nissan using a different bias voltage nowadays?

Evidently they have changed. I drove the car and ran all the monitors=OK. They want me to run them again just to verify. Did this before and it did not fix it.

I don't think they know how to fix it either. I believe its a programming issue. Time will tell.

Wanted to update this. I had a week off while in Training for Automatic transmissions so....nothing got done.

Before I left, I redid the exhaust and intake smoke tests cold per Techline recommendation. Found two very small leaks on the exhuast so small in fact the smoke was not visible but I could hear something. Soapy water to the rescue. Fixed those.

On the intake the TB gasket was leaking, had to order. After I came back from training. Today I put on the new TB gasket, found the old one oddly smashed in one spot. This fixed the intake leak.

Cleared self learn, did idle air learn, test drove. The data was EXACTLY the same as before. The BANK 1 Sensor 2 02 sensor just sits at around .47-.50V all the time at highway cruise. The ECM tires to adjust with the A/F Adjust PID. A/F sensor and everything else looked fine. It set the P2096 code much quicker than it did before so hunting the VERY small leaks did NOTHING. I redid the Active fuel test and all 02's and A/F's work as expected. Techline recommended that I replace the ECM if fixing the leaks did nothing to correct the situation.

As I found before NO ECM reprogrammings are available. I'm tempted to do voltage drop testing on the wires going to that 02 and also check for any bias voltage from bank to bank 02's and see if they are similar. That being said they did work perfectly find during the Active fuel test so one would think the wiring integrity would be ok.

This kinda goes back to the beginning of this. I felt it was a programming issue and it may well be. IDK, this is a very odd one.

FIXED!!!

I ordered and replaced the ECM per Techline recommendation. THis fixed the issue.

BIGGEST change was when cold the 02 sensor BIAS is 1.78V!!! Anything other than that on newer Nissan's is wrong apparently. Test drove, ran all monitors OK, fuel trims and everything else looked perfect, even slightly better than before. A/F adjust readings stayed very low as well. The issue was ECM logic not programming but I was on the right thought path from the get go.

Funny how they sent me on a wild goose change with hunting small leaks and replacing parts that fixed nothing and I said would not. Oh well, its warrently.

Hope this helps some of you in the future. FYI, Nissan does not five a bias spec. or anything like that in the service manual. My biggest gripe with them is the lack of good data/references in the manual. Makes it fun sometimes.

Thanks for the FIX update! I've been super busy this week, but following your updates the whole time.

I. Have. Questions.

BIGGEST change was when cold the 02 sensor BIAS is 1.78V!!! Anything other than that on newer Nissan's is wrong apparently.

Hah, I KNEW that was screwy! :lol: So, 1.78V is the new 'good' bias voltage, then? Can you provide an estimate on what model year that might have changed?

Funny how they sent me on a wild goose change with hunting small leaks and replacing parts that fixed nothing and I said would not. Oh well, its warrently.

See, I'm super surprised they didn't suggest changing the ECM earlier. :silly: I feel like GM or Chrysler tech lines would have thrown an computer at this long ago. I figure that the high degree of uncertainty around this code has a lot to do with this:

FYI, Nissan does not five a bias spec. or anything like that in the service manual. My biggest gripe with them is the lack of good data/references in the manual. Makes it fun sometimes.

A/F adjust readings stayed very low as well.

Any idea on what a 'good' range for these PIDs would be, based on your experience? Just trying to get a feel for this PID before these vehicles fall out of warranty, and become my problem.

I had a week off while in Training for Automatic transmissions so...

Off topic, but... Are all the things I've been hearing about Nissan CVTs true? Does aggressive fluid changing make ANY difference? :huh:

I would say the 1.78V is good on anything newer such as the 2013 and up Pathfinder, 2013-up Alitma, definitely the Murano 2015 and up.

I agree with the uncertainty with the code. They seemed to grasping at straws a bit.

I don't have a PID spec for the bias voltage. I think the A/F adjust reading should stay under .100 + or -. Common KG readings I saw where about -.058 for example. This is how I knew it would set a DTC before it even did it. Anything above that and if it keeps climbing will set a DTC over time.

The CVT's have a LOT of issues. Reprogramming them has helped. Most of the wear is due to the older programmings and failures. I don't think fluid changes will do much to help. That being said if it where my car, I would doing a drain and fill on it every 50K. DO NOT DO ANY KIND OF FLUSH. YOU MUST USE NISSAN FLUID NS-2 or NS-3 as required. Anything else is detrimental to the CVT.

93Rubie wrote: The CVT's have a LOT of issues. Reprogramming them has helped. Most of the wear is due to the older programmings and failures. I don't think fluid changes will do much to help. That being said if it where my car, I would doing a drain and fill on it every 50K. DO NOT DO ANY KIND OF FLUSH. YOU MUST USE NISSAN FLUID NS-2 or NS-3 as required. Anything else is detrimental to the CVT.

Gotcha, thanks sir. I've got a family member with a Versa, wanna stay on top of any potential issues if at all possible.

I would say the 1.78V is good on anything newer such as the 2013 and up Pathfinder, 2013-up Alitma, definitely the Murano 2015 and up.

I don't have a PID spec for the bias voltage. I think the A/F adjust reading should stay under .100 + or -. Common KG readings I saw where about -.058 for example. This is how I knew it would set a DTC before it even did it. Anything above that and if it keeps climbing will set a DTC over time.

Love it. Valuable stuff here.

While we're talking about trims and O2's, could I get your assistance on a vehicle that's been eating my lunch? :blush: '05 Altima 2.5L with a P1273 that just won't be fixed.

www.revbase.com/BBBMotor/TSb/DownloadPdf?id=126316 . have you seen this bulletin? you probably have!

cheryl hartkorn wrote: www.revbase.com/BBBMotor/TSb/DownloadPdf?id=126316 . have you seen this bulletin? you probably have!

I have, but it only applies to the 3.5L. Good thinking, though! There are three other TSBs for this code that I'm aware of - one says to replace the downstream O2 (which I have), one talks about looking for exhaust leaks (which I did), and another that reminds you to do the self learn reset after repairs (done multiple times).

Been awhile since a Nissan gave me a hard time.

Is it actually shifting the 02 that is? Is the A/F working correctly?

Nissan does use the downstream 02 for some fuel trim. It will compare it to the upstream as well.

Was it replaced with a OEM sensor? Aftermarket stuff is a crap shoot as you well know. Heck, getting the right OEM part can be fun.

I used the Fuel Injection % test to control trims. The rear O2 goes rich at 6%, and lean at - 1%. I don't have the scanner with me, otherwise I could post captures. I swapped in a new A/F sensor today, no help.

The thing that bothers me is how the code always sets during highway cruise. The rear O2 reads .6 to .7V, but the O2 Monitor PIDs says 'LEAN'. I believe this is the root of the issue, but can't figure how to make the rear O2 happy. :silly:

The downstream replacement was a Bosch that cross-reference to the part number specified in the TSB. NOT the same thing, I know. We've got NTK and Denso sensors coming for tomorrow.

Recently picked up a 2015 Murano SL with 51k on it for the wife, and I've got the P2096 blues as well.

Started with replacing the air filter, as the existing one was pretty dirty, and the air box had debris in the entry hose. Cleared codes, and the CEL stayed off for about 3 days. Popped back up this morning.

I'm tempted to replace the O2 sensor, but admittedly, I've got no experience with troubleshooting Asian cars...all my diagnostic and repair work has been related to my diesel BMW, where I have the convenience of using the dealer-level software.

Fingers crossed it's just a sensor! I'm bookmarking this post in case it gets more involved!

Very good info here thanks for posting in detail