Mazda MYSTERY No One Could Solve - Part 1 (P219B - Bank 2 Air-Fuel Imbalance)

I have a feeling this one won't be easy...
This 2015 Mazda CX9 has a persistent Check Engine Light at 80k miles.
Dealer already performed a SKETCHY "harness repair" which involved chopping off and re-routing the harness for the Bank 2 Air Fuel Ratio Sensor... Amazing haha xD
Code set: P219B - Bank 2 Air-Fuel Ratio IMBALANCE.
What does that mean??
Let's start from scratch, collect some data, and come up with a game plan on what exactly to test on this Mystery Mazda. How would YOU diagnose this car?
THINKTOOL PROS:
www.amazon.com/dp/B08XXWHQVJ?...
Enjoy!
Ivan

[@andybonneau9209]

AFR is often determined by DOWNSTREAM sensors as well. Swap the downstream sensors . Also, a localized vacuum leak on the intake can cause an imbalance so smoke check it.

[@somerandomguy3868]

I was thinking intake gasket

[@InsideOfMyOwnMind]

Agreed. I would start by swapping DS1 and DS2 and get them out of the way then go after leaks. After that injector flow rates on bank 2. Even though it runs well it can still be lean enough to get the PCM's panties in a bunch.

[@johnleinen7167]

Went thru this on a Chrysler, down stream sensor switching slower than opposite bank due to a catalyst with a very small Crack in middle of the substrate, had to verify it with a boroscope camera.

[@jackmay1728]

i was thinking slight injector leak on exhahst stroke

[@jackmay1728]

right track wrong event

[@kennethking2301]

The first thing I would check on would be the accuracy of the repair performed by dealer from the TSB. I looked it up and there is a TSB for 2011-2015 CX-9s with that DTC. The TSB says to separate the A/F sensor lines from the emission harness by installing a replacement short cord service part. The reason for this is because the A/F sensor lines were being affected by abnormal electrical noise from the other wiring in the emissions harness. If the dealer did perform the repair correctly, the most interesting data point for me is the bank 2 fuel status indicating "engine off" instead of closed loop. I think I would check the wiring diagram to attempt to locate that signal.

[@Walczyk]

Yikers

[@PineHollowAutoDiagnostics]

I actually couldn't find that TSB...what's the TSB #?

[@kennethking2301]

@@PineHollowAutoDiagnostics I found it on the NHTSA website. static.nhtsa.gov/odi/tsbs/2015/SB-10099785-2532.pdf

[@David-lq2xg]

@@PineHollowAutoDiagnostics Bulletin No: 01-006/15 MIL ILLUMINATION WITH DTCs P219A:00 AND/OR P219B:00

[@throttlebottle5906]

@@PineHollowAutoDiagnostics Bulletin No: 01-006/15

[@htownblue11]

I’d swap sensors between banks. If nothing changes, I’d look towards injectors. If you had a leak in the manifold at the right location it might only effect that bank. Ultimately we have to find if the computer is receiving incorrect data, or if there is a cause for the data to be how it is.

[@jackmay1728]

the computer is too damm smart is reporting what its doing AFTER seeing a rich event its taking fuel away yes a vac leak could do same but ivan smoked for vac leak none found if fuel trims were zeroed and you were quick enough on start up you may see a rich pid on scanner maybe but the computer is taking fuel away

[@davidgrisco1939]

The next thing I'd look at are all the sensors to see if any OEMs were replaced (with aftermarket).

[@WyGuyyy]

At Lexus we had a service campaign for an air fuel ratio imbalance code. It would set due to an improperly sealing exhaust valve.

[@juanojeda8069]

Oh so what I do my Lexus Rx 350 2014 had this code but running good

[@tanaseav]

Of course it's an injector, the error description seems pretty clear. One of the injectors on bank 2 is dripping like a garden hose. EIther test them or move them to bank 1.

[@marlu6373]

mai tanase daca un injector is leaking like a hose trebuie sa se simpta ca motorul nu merge rotund

[@jeffryblackmon4846]

​@@marlu6373 Romanian to English: "even better, if an injector is leaking like a hose, it must feel like the engine is not running smoothly" for those who wish to know what mar lu wrote. My response: Este o idee interesantă!

[@marlu6373]

@@jeffryblackmon4846 looks like you know romanian or the good new google translate

[@boomer9900]

The main thing is determining if there is a sensor problem or not. The plugs can be inspected to see if there is a rich/lean on one bank or cylinder. Is the exhaust backpressure equal or is a cat problem? (not sure if there are cats on both banks or not). Then there are the injectors. A flow test would reveal a bad injector. But remember that per the documentation this is a cylinder to cylinder and not a bank to bank code of course taken with a grain of salt when it comes to these things. Definitely the downstream stuck sensor is a great place to start. General engine mechanical like compression would be next. Sometimes it helped me to force the computer into backup strategy by disable the maf and see what is up. This is a weird one.

[@PineHollowAutoDiagnostics]

Great suggestions 👍

[@Doomster9]

I had a 2009 Corolla with the same AF Imbalance (Bank 1 of course) that turned out to be a burned exhaust valve in one cylinder. It ran perfect, had no misfires or stumbles, but it failed the leakdown and replacing the valve solved the code. Just another path in case you sensor theory doesn't pan out.

[@PineHollowAutoDiagnostics]

Burned valve on a Toyota? That's impossible! 😅

[@Doomster9]

@@PineHollowAutoDiagnostics Shhh, don't tell Scotty!

[@luigigonzalez5062]

We all know that burnt valves is the aftermath of REV UP UR ENGINES! 😄🤣😂

[@keltecshooter]

This reminds me of a Jeep with a pentestar engine, similar codes, had wrong/defective/non oe rear o2 sensor. Wasn't a Chrysler sensor so that gets my attention immediately. The suspense is killing me now 🤣

[@juanojeda8069]

Jeep Rams ect. Need to be OEM parts of they give trouble

[@vpimike2646]

The disagreement between the two upstream O2S's seems to stand out to me. I would agree with your suggestion to swap them and make sure they are of the same make and part number. I like your fun little cliffhangers, Ivan.

[@deviatorst]

Start with the basics. 1. Check that TSB and more importantly, its implementation. 2. Exhaust leak between sensors. 3. Swap sensors bank to bank, as you suggested. 4. You could compression test a cylinder or 3 and compare them bank to bank.

[@lvsqcsl]

The last time I felt the way I do now is when Larry Hagman's character J.R. Ewing got shot on "Dallas" in 1980 and I had to wait an entire summer to find out who did it. I hope I don't need to wait long to find out what is wrong here. Great video!

[@pigyear88]

my experience with mazda was intake air leak on bank 2, very tinny leak, but I used teflon tape to tighten the O-ring gasket seal. no more issue(engine light) over the past year.

[@GraditelMacedonia]

Like you mention... firstly change places on downstream sensors, take data, then change upstream sensor and also take data for differences.

[@joebucci3408]

Almost every time I had that code it's fuel injectors. Also make sure there's not a lot of fuel in the oil. Block off pcv and drain and fill engine oil.

[@jakeandrus690]

The code description was for a cylinder imbalance on bank 2, not a bank to bank. I'd start by doing an injector balance test and go from there 😎

[@NamesAA]

I would bust out the propane next. Id look at those same pids and enrich the intake, just to work the AFR and downstreams to make sure we don't have someone lying. Next I would defeat the PCV somehow, usually removing the breather hoses, and pump some propane in the dipstick tube. If your trims straighten out with the propane in the crankcase, it has an intake leak. If that doesnt do it, I also suspect an injector issue. This mazda might be able to run the ford IDS injector balance test with the scanner. Exhaust leak near an AFR/Downstream o2s is also possible. Depending on how much ford is left in this mazda, the downstreams might have a large effect on fuel trims. Also that wonky harness repair, I need to see that TSB. But as you said, the AFR does appear to be working.

[@ehsnils]

I would have started with checking the spark plugs since they can tell you a lot about any possible imbalance instead of perceived imbalance by the system.

[@davidcooper8840]

Ivan you are a great mechanic/diagnostician. Thank you for all of your efforts.

[@EDP1]

am gessing there are very little good mecanics that understand modern engines . you are a genius .

[@clueless6559]

That code Ivan as you have read is for cylinder fuelling imbalance between cylinders on that particular bank , its very subtle and the wideband sensor plays a key role, good luck..

[@sanger440]

That wonky rewire job show at the beginning is got to be the culprit along with non oem sensors. Start there for sure.

[@joshboyer8449]

You and scannerdanner are my go to guys, such great detail and knowledge

[@markket1154]

Good case study looking forward to part 2

[@lvsqcsl]

One thing I have noticed in videos you and Eric have produced recently, you all are specifying OEM parts. Great video!

[@ghettsumm7949]

Temporarily introduce some flammable Brake Clean to the bank 2. and observe the changes.

[@terrya6486]

I would go measure the resistance on that TSB rewiring. See if you have a different impedance in that particular piece of wire that was added for the TSB.

[@Alpha06R]

Swapping the HO2S is a good idea. I don't think is a timing issue, considering it doesn't have P00xx errors. I will check if Ford have a different approach to this issue, because this is a Ford Cyclone engine (yes, the one that have the Water Pump driven by the Timing Chain) and I believe they share the same PCM. Edit: Ford Test Procedure for this error has more information regarding Resistance and Voltage on the HO2S than the Mazda Procedure. And yes: Same PCM, and almost same CAL ID.

[@andrewcimochowski]

I would probably check to see if the air fuel ratio sensors are the correct part number for the vehicle…

[@jtjones4727]

That's often times not possible, usually they don't print any visible numbers/letters on O2s and A/F ratio sensors.

[@mistsemy1522]

Eagerly waiting for part 2

[@edwinlomonaco6754]

I would do a relative compression test. Then possibly go in cylinder on bank 2. Possibly an engine fault on bank 2 causing that bank to run rich. Thus pulling back fuel.

[@MsFireboy2]

Thanks Paul excellent presentation as always. I really enjoy watching your videos.

[@PineHollowAutoDiagnostics]

Which Paul? :)

[@MsFireboy2]

@@PineHollowAutoDiagnostics Sorry Ivan. My bad. I really enjoy your videos. I retired about 20 years ago from the business. Would like to see more CAN bus diagnostics? Thanks.

[@OneLegged-honda-mechanic]

I'd propane enrich to see if the b2 downstream sensor has the ability to report high.

[@bonedaddy4670]

The best course of action based on the presented data is to wait for the part 2!

[@jimgale8465]

So years ago, Champion Parts Rebuilders used to have a plant in State College.... they remanufactured automotive parts.... Electrical, water pumps, carburetors, clutches, etc. Most likely they are gone, I sold and installed an automated vertical shaft grinder (30 hp) that would re- surface clutch pressure plates and center plates for automotive and truck clutches. It was so long ago I'm not sure the building still stands, but they employed maybe 200-300 people. Just a FYI- love watching your work, BTW.

[@PineHollowAutoDiagnostics]

That would be so cool if they still existed!

[@chadgardee1496]

Man Ivan so smart he looks at stuff that I would look past

[@baxrok2.]

Interesting. Thanks Ivan!

[@rjm7168]

1. Verify B2D sensor is good. 2. If O2 sensor is good, back probe it to verify ECU is correctly reporting the voltage being generated by the sensor. 3. If voltage at sensor is different than what ECU is reporting, verify sensor and ECU grounds are adequate. 4. If grounds are bad, fix and recheck. If grounds are good, or fixing them does not fix the problem, I would suspect a bad ECU but before condemning, continue with step 5. 5. Check for vacuum leaks on bank 2. If found, fix and recheck. 6. If problem persists, verify correct valve timing and phaser operation on bank 2. 7. If no timing issue, or fixing it doesn't resolve the issue, replace ECU.

[@PineHollowAutoDiagnostics]

Interesting Flow Chart... :)

[@georgebeuselinck9255]

Suspect the wiring harness change and the oxygen sensor (not factory?)

[@dutchmiller704]

If I could I would so I will wait for part two.

[@MC-om7ds]

Well personally I would start loading the parts canon beginning with the sensors because they are the cheaper parts and because I have no clue how to go about diagnosing a vehicle. That’s what you’re here for hahaha luv u Ivan keep up the great work

[@dans_Learning_Curve]

Most of your videos I follow along very well. However, this time, I got lost. Awaiting part 2.

[@robertoruiz7069]

I love these video's on these crazy jobs ,IVAN. i'm only halfway watching ,but I'll take a stab at it,to see if i can guess. when you read the causes i guessed if the engine has a plastic intake manifold,my thought is could it have a crack in one of the runners going to a cylinder making THAT CYLINDER LEAN.But only affecting a single cly.therefore they Assume that will set a code.Also then what if the intake gasket right at the manifold to the head was ONLY leaking at 1 cylinder? or could the computer THINK a fuel injector IS not operating as good as the rest of them? therefore trowing the code? just guessing,thanks

[@griffith04]

If they fixed the harn3ss for oil wicking then maybe b2s2 O2 is still being affected and skewing its reading. Need to inspect harness above valve cover to check for oil in connector. Oil pressure switch can leak into harness.

[@10100rsn]

6:25 So, basically the computer doesn't know which sensor is giving correct information, upstream or downstream, and after trying and failing to correct for the bad one it blames the good one?

[@dharley189]

Yes. I would try swapping sensors between banks if not too tough. Compare ground voltage drops Cross fingers and see if any good KZbin videos from PHAD that could help ‼️

[@amjadzidaoi4011]

I suspect faulty fuel injector in bank 2 causing long-term reading rich.

[@46bovine]

My next step would be to contact Pine Hollow Auto Diagnostics. I would be lost at this point. Great video, Ivan, what the heck is the problem?

[@Jpilgrim30]

I had this code once on a newer Silverado but it was just due to someone putting a cheap oxygen sensor on. I was surprised as well to see that they are also detecting imbalances between cylinders on the same bank.

[@mikechiodetti4482]

Swap the downstream sensors also. That upstream has what looks like a lot of noise on it's output. Possible alternator diode bad? Scope time.

[@davidmelbourne5480]

So many possibilities! Swaptronics first of course. The tiny currents involved in those sensors means the wiring/connections are always suspect. Beyond that, intake or exhaust leak, injector prob, valve leak/timing. Who knows, even a partially blocked cat (if each bank has its own). A few more tests needed. The propane one mentioned below could be useful.

[@randy1ization]

very sensitive systems..

[@deniscarr469]

I think I would persue the ''engine off'' message first. That might be the sprat that catches the mackerel. British idiom, but I think you'll gather what I mean.

[@jtjones4727]

I'm not as used to working with A/F ratio sensors as much as good ole O2 sensors, but this kind of seems like a stuck or skewed low Bank 2 Downstream sensor. But then again, I do see it jumping up to near .7 Volts sometimes. I'm also kind of lost at this point, as to where to go next. Also, what kind of PCV system does this have? Does it connect with a single bank, or both banks?? The computer seems to think there is a minor rich condition on the affected bank, maybe check your injector waveforms on the bank in question. Maybe there is a slight mechanical issue with one injector. Possibly sticking open a hair too long or something.

[@Gromitdog1]

Pull the plugs and read them, thinking injector malfunction or vacuum leak.

[@PineHollowAutoDiagnostics]

Great suggestion! Spark plug analysis is still relevant even on modern engines 🙂👍

[@mrfishbulb7187]

Double check that wiring harness hack job and the relevant TSB details.

[@JoseSilveira-newhandleforYT]

Everybody loves a good mystery, and this one has some exotic ingredients :-) I'd swap sensors and check if the rewired AFR is the right part (why did they rewire?).

[@larrybe2900]

Service bulletin for interference with the wires.

[@JoseSilveira-newhandleforYT]

@@larrybe2900 🙂

[@somerandomguy3868]

At first I was thinking intake vacuum leak but now I'm leaning towards faulty sensor, these are so sensitive I could easily believe one or more are out of spec

[@johnloira7932]

Cylinder imbalance codes as you see here are used by the ECM to pick up slight variations in combustion depredation using either the AF sensor or the Crank Sensor. The ECM looks at the engine as 6 single cylinder engines and compares each cylinder to each other to see how it is running. It does this by closely monitoring the AF sensor for each cylinder exhaust pulse and the crank sensor. If it sees a variation in a cylinder as compared to the other ones it will set the Cylinder Imbalance code. Even though the engine seems to be running good, there is something wrong with the combustion process that the ECM is picking up. Now this could be due to a number of things, but the most likely cause is an engine mechanical issue, such as a valve starting not to seal so cylinder compression is slightly lower than the other cylinders. Best bet is to perform a compression test and a cylinder leak down test and see what the results are. Code may also be set due to an underperforming injector, hence the rich condition as the ECM is fattening up the injector pulse to compensate for the lean condition, but I,m not sure if Mazda engines can do bank to bank fuel correction. Looking forward to part two

[@Stambo59]

I would be tempted to swap the AFR sensors if they are easy to get at. That way if the problem moves it's the sensor, if it stays on bank 2 it's time to look further. Perhaps do the same deal with the downstream sensors. With an imbalance between banks it should be something that affects bank 2 only. I may be wrong but I don't think a vacuum leak would make such a big change between banks, it should get better as the load/revs increase. And as has already been mentioned, check the work done by the dealership, although it seems the problem existed before they started on it. Edit: I read the comments after posting mine, It seems many people have the same thought you did about sensor swapping.

[@cclngthr]

Mazda doesn't have the o2 sensor bias voltage, but I would check to see if it now does have that. Swapping the o2 would be my start, plus using the Pico oscilloscope to verify the readings are what they should be. If the upstream sensors are faulty, I would replace both with new OEM parts just to have the readings the same, then go from there.

[@timbo19751975]

Could you force the engine richer with a propane torch and see if both sensors report richer to the same degree? If possible switch the sensors around and compare results....

[@mikefoehr235]

I have no idea what could be wrong. I wait for next episode.

[@arsinoeivlostprincess4228]

Swap the sensors around. I see carbon forming on valves and making a restriction on di engines. Maybe the vapors enter on that side of the engine and create more coking. Some engines have flappers inside the manifold to make long and short runs. Maybe one is stuck. Vacuum hose leaks. Bad wire or corrosion on the o2 sensor connections or elsewhere. Could be a flood car. Yes smoke check. OMG I'm not even a mechanic I just watch these kind of vids 24/7/365 There is a lot of value in it.

[@miguelacosta9780]

I agree with some of the tech look for a exhaust leak between the sensor and the exhaust manifold,

[@Lbjsmorris]

For this code I look at computer commanded pulse width for each injector on bank 2 to determine odd cylinder. This would narrow down to which cylinder is likely causing the imbalance. Think of this code like a minor misfire. The pcm is able to determine the air fuel ratio of each individual cylinder from the air fuel sensor. On Chrysler products I have seen worn lifters and leaking injectors causing this code. I’m a Chrysler dealer technician so my answer may be helpful but off at the same time.

[@PineHollowAutoDiagnostics]

Very interesting suggestion. Is there a specific data pid for each CYLINDER pulse width, or just B1 vs B2 pulse width?

[@Lbjsmorris]

Yes, there should be data pids for each individual cylinder fuel injector pulse width. Looking forward to seeing what you find for causing the code. I enjoy watching your channel.

[@Lbjsmorris]

Now that I’ve seen part 2 the pulse width on cylinder 2 would have been lower indicating the pcm seeing a rich condition on cylinder 2. This would have me flow testing the injector next in the diagnostic process. Different approach for the same result.

[@thejoneseys]

The harness improvement looks anything but 😁 Firstly i'd have to verify that sensor they installed is actually OEM or a knock off special. Trust but have to verify. Depending on how easy access is I'd swap the up and downstream sensors across banks and measure again. Wasn't impressed with the diagnosis process on All data 🤦🏻‍♀️

[@v8motors.]

First I'd check that TSB to see if it really is recommended to chop off the original wiring harness. Seems strange to me.

[@Alpha06R]

There is a TSB of that it seems. Not sure if it applies to 2015, but it does applies to the 2011-2013.

[@jtjones4727]

Yeah that is a strange one. Since the widespread adoption of CAN Bus and twisted pairs of wires, well this whole thing about "interference" just sounds odd. I'm not saying it isn't possible though, just a new one on me.

[@frizzlefry1921]

@@jtjones4727 I fixed a car audio system with subwoofers a guy had installed. Complaint was everytime he hit the brake pedal the subs thumped very loud. Problem was the routing of the signal wires literally moved a wire 3" over in one spot and problem solved.

[@patrickcoakley1328]

Any plans to visit NJ? There is an old Porsche patiently waiting for you!

[@PineHollowAutoDiagnostics]

You might have to bring it to me 😉

[@scotts4125]

I had 3 CX-9's kept each one 3 years. They were probably the best vehicles I have ever owned. The only issue I ever had was one needed a brake booster which was covered under warranty. Nothing except oil changes. I now have a Kia SX Sportage (turbo). What a piece of junk compared to the Mazda's. Looking forward to final diag and fix on this.

[@izukenekuzi]

forget the car, i want a front yard tour, looks beautiful 👏

[@chronicle838]

Smoke machine up the tailpipe and look for bad welds or fine cracks in the bank 2 exhaust between the upstream and downstream sensors. A stethoscope with an open hose may also be helpful to pick up on an exhaust leak in this area.

[@AP9311]

Well, having watched this two times, I'm not sure what would be my thought be..... maybe faulty PCM or bad or incorrect software in the pcm. You didn't say about clogged systems, i would say... maybe wiring messed with. Like someone else commented, TSB recalls? I'm not that good of expert like you are! Those suggestions are my thought as of now. Hopefully, you'll provide a result that everyone didn't get the correct results!

[@kyletuttle9064]

Waiting for part 2 had same on a Tahoe this week and replace a downstream O2 sensor.waiting to see same kind of data.let us know Ivan.thanks

[@hpelisr]

I think to go back to the first part of probable cause page, and check some of the outlined cause a little closer.

[@russellhltn1396]

I think one of the sensors are whacked. Perhaps aftermarket. But I wouldn't rule out a green crusty shifting the voltage. Swapping sensors seems like a good plan.

[@dyizhere]

Swap O2 sensors if possible. See if the problem follows.

[@jeffreygoss8109]

That’s what I would do, although in the north replacing these can be a PITA

[@doctordiesel5467]

Had injectors cause this on many different vehicles including fords another issue ive found at times.over looked is intake manifold runner control plastic fins with pieces broke off And also carbon coated valves causing lean conditions on specific banks aswell as caused rich codes also but ya id tey a quick sensor swap see if the problem remains where it is

[@richarde.beatty838]

start with a smoke test of intake manifold etc, along with inspect the integrity of the sensors, OE? or aftermarket, repair the sensor wiring to OE, then switch the sensors to each others position...

[@cichlid43]

Been seeing this code on newer Toyota 3.5 v6 with little bit low compression from worn valve guides

[@adamtrombino106]

I have seen injectors cause imbalances, BUT good point on the switch rate on the upstream o2s.. Suspicious...

[@DIYDaveOK]

Any knock-off sensors on that bank? Squirrely data like that, along with yours and Eric's prior history, shows that's got to be at least a suspect for bizarre behavior like that.

[@PineHollowAutoDiagnostics]

We'll check that in Part 2 👍

[@lvsqcsl]

Oh, the pressure is on, MY FOOT! You'll figure it out, Ivan. I haven't even watched the video yet and know that. It is a 2 part video, however, so, this will be interesting.

[@mykofreder1682]

Swapping is a good idea, I would prove the air or fuel flow going into that bank is normal. A computer dealing with an air flow that is too high or fuel flow that is too low because something is broken or blocked in that flow.

[@pensiveintrovert4318]

I was under impression that negative current on wide band upstream sensors means RICH, not lean. Maybe confirm that you're right. This would correspond to down stream sensors voltage being higher, closer to 1 volt. The ECM is doing the right thing by taking fuel away.

[@GraditelMacedonia]

Yes is confusing!? probably you have to focus on bad oxygen sensor...some small leakage of air or gasoline from injectors on that bank, but that will be after changing sensors what im writing previously. Writing after...now came to my mind... also slightly misfire or bad coil/plug can trigger that

[@jeremyah78]

I haven’t watched part 2 yet. Sooo, I would be curious of what b2 a/f sensor looks like with the scope. If it shows slow response, matching scan data, I think swapping front sensors is an ok idea, IF bank one is easy enough to get at… OR I’d be checking injector flow rates (whichever seem like the easiest. IF scope patterns of the front A/F looks more normal, and LESS like the slow response on the scanner, I’d want to compare the same signal at the computer… my theory being that there’s potentially impedance post the “TSB” wire job. Now for part 2🙂

[@RussellBooth1977]

I would just swap the sensors over to isolate the problem but I had a similar problem in my Holden VY SS Commodore which runs the 5.7 litre Chevrolet LS1 V8 engine albeit with no fault codes after I drove through flood water where water 💦 somehow got into the fuel tank, caused lean fuel trims, hesitation on acceleration after starting up & when I reversed out of a car park after the engine had been sitting for a while it started to idle rough until the water got stirred up inside of the fuel tank. I run 94 Octane E10 unleaded fuel which does absorb water 💦 & I did add a litre of methylated spirits to the fuel tank but maybe I shouldn't have bothered because that's 97% ethanol anyway but just driving it fixed the problem until there was no more water in the fuel tank. The fuel trims were over 10% on one bank & something like a couple of a percent on the other,now they're both sitting nicely at -1.6% LTFT on both engine banks ! H

[@josemontes9050]

I will look for restriction in the cat for bank 2, check with a in pressure transducer to both banks and compare.

[@kentbetts]

I think this Toyota mechanic said that the downstream sensors are more for checking the condition of the catalytic converter rather than engine control. Anyway, here is the excellent video. kzbin.info/www/bejne/m5q8Ypl-mKmkq5I

[@josemontes9050]

@@kentbetts What can I remember, Scanner Danner and his brother has video with a case where the downstream sensor has an effect with the fuel trims.

[@hikerJohn]

Thanks professor :o)

[@Nymi5]

Disconnect the downstream sensors, and see if the trims go better... could downstreams be cross connected, because thats what it looks like.

[@boilertech44]

Is there an injector that is adding more fuel to bank 2 and the systems trying to correct it?

[@danekeeper1]

manufactured data, get the raw data obd to confirm data. then get cold beer and go for a nice fishing trip!

[@anthonyvon4531]

Unless there's a PCM issue I'm surprised it tripped a code because usually the tolerance is set pretty high.

[@canadatransistor]

are the rear o2 sensor wideband or old school types? I suspect they put a wideband where an old school is maybe supposed to go. It's probably sending 0 current to pcm because it's stoichiometric and being interpreted as zero volts by the pcm. I would check if the wrong part could plausibly fit the connector despite being wrong part.

[@Coolbreez101]

Great video and responses comments guys I have that code I changed the downstream sensor and that code cam back any more suggestions I would appreciate you guys input ?

[@PineHollowAutoDiagnostics]

Why would you change the downstream O2 sensor? Did you watch the video? 🤔

[@Coolbreez101]

I changed the sensor closet to the top where the engine is by because I had a code p0420 at first now the code is p219B on my 2012 cheavy traverse Lt

[@Garth2011]

Did the check engine light come on during the test drive? Maybe ohm the sensors first to see if they are in range then move ahead.

[@montestu5502]

I would check the wiring on the TSB repair harness. Kind of seems like two wires got swapped and it’s reading backwards.

[@Mako-sz4qr]

I would head to a wiring diagram and verify those wires they chopped off first. Then yeah switch sensors then back to the live data check.

[@belowzeros]

they hacked that harness up, did they change anything else like the sensors?

[@teekay_1]

One of the sensors has to be wrong. I don't think it's an engine/cam problem, it wouldn't be working that well. Other people have said it, but the two clues are (1) dodgy harness repair (2) "changed sensor"