Test Your Lean P0171 / P0174 Diagnostic Skills-Pt5

We finally have a major break in the case here...
Part 1 of the series is here:
• Test Your Lean Conditi...
Part 6 is here: • Test Your Lean P0171 /...

[@taskhunters5245]

I too could not believe you were not in first 10 Top automotive chanels on YT back then. Eny way, I have watched and try to understand your fuel trims and wide band O2 sensor videos and now while diagnosing my 2011 4 pot qashqai managed to determine I had hole in my intake pipe but I don't quit understand why 4wire O2 sensor does es not mater that diagnostic tool I use takes as wide band sensor and displays EQ ratio and voltage instead normal O2 readings. I am almost sure this models used standard O2 sensors... Thanks and I can not thank you enough for doing this videos.

[@SchrodingersBox]

Thank you. I believe the fact I am a DIY is a major reason I’m never included on any top channel lists.

[@DJDevon3]

So this is all going to boil down to a common vacuum leak affecting both banks isn't it? I can see the light at the end of the tunnel. Regardless this is a great lesson because it's real. This is as real as it gets. You are showing all of your successful diagnostics along with your failures because that's how science works. I'm loving every second because this is again, gaining education and experience at the same time. This is unadulterated education (for everyone) in its most raw form. You can't buy this stuff in stores you have to live it. Can't wait for the next episode.

[@SchrodingersBox]

***** Yes I think this series is incredibly important- see how a misdiagnosis could easily have been made because of a miscommunication with the scantool and you would never know it. It is critical we understand this so we can potentially identify this issue. For the 7 years I have been doing this I have used enhanced parameters on EVERY car I ever diagnosed and I never knew that there could be a potential miscommunication like this. But there is something wrong still that suddenly enhanced parameters are not working on my car all-of-the-sudden. Need to figure that out.

[@SchrodingersBox]

***** Devon also remember that in Part one, FreezeFrame did show B1 at +24 and B2 at about +.8. So still not so sure there isn't even internal communication issue or something. "That don't make no gotdam sense!"

[@DJDevon3]

Schrodingers Box Best thing to do is contact both AutoTap and AutoEnginuity and ask how something like this could occur. If anyone would know they probably would. I actually tried looking up the SAE/ISO for enhanced GM data (likely GMLAN) but there is no such standard. It all depends on the OBD-II protocol. You would have to learn the inner workings of the protocol but that's beyond the scope of what a mechanic should do. That's your scan tool manufacturers job so they have the engineers that specialize in those protocols. Not just anyone can make a scan tool software like that which can pull enhanced data. That's a very advanced feature to have so they have engineers capable of handling that question.

[@SchrodingersBox]

***** Thats a fantastic suggestion- I will do that before next video for sure. It's just that this phenomenon is a recent change so something must have changed either with BOTH scantools OR with my PCM's ability to communicate enhanced PPIDs all-of-the-sudden. But damn does this not make you think twice when using enhanced scan data as a habit like I have done for 7 years now?!?!?!

[@DJDevon3]

Schrodingers Box It sure does make me think twice. Perhaps you've been using it wrong or relying on enhanced data too heavily the whole time. Most videos I see of people using OBD-II scan tools to pull up enhanced data usually show issues with the data. Ford Mode 6 is a great example. Most scan tools have a really bad time with enhanced live data. I think you've been getting lucky with using it but regardless it was always working for you and now it's not. Something changed. Could be as simple as a pushed in pin on the OBD-II connector. I think you having the laptop on the engine is a bad idea since RF can interfere with signals especially if it's near the distributor or ignition wires. Also not good for the laptop to sit on a hot engine. This might sound stupid but is there a way to test the integrity of the data cable you are using. Continuity tests? I hate being a parts changer but you might want to find another cable to rule out data transmission issues of the cable especially one that's been sitting in a hot engine bay, computer cables are not designed for automotive environments there's no RF shielding.

[@spinb]

What a great series. Almost every little problem I've had in my 01 Navigator has been like this -- a mystery. I never have straightforward issues with my car.

[@ibeemeeintp3033]

Being a logician I really enjoyed this series very much 😎👍

[@shaishavshah5114]

Hahah...i liked the topic of substitution of value . M an electrical automation engineer...i deal with controller programmings and all and have had stuck with this sort of frustration before .. weird things are normal in automation..but m quite happy that i joined your video series and that I can't resist watching you scratching your head for these issues...keep this continue...m new with car automation but seems involving....

[@whirls007]

Thanks for all the info. Been listening for hours on P0171. Will have questions soon. Thanks.

[@clutch5sp989]

Couldn't believe just how many dum-bass-holes on YT will get views by many hours of mouth explaining ST & LT fuel trim and how it all works. They provide absolutely NO help or even show what normal numbers are or should be. Matt is the guy to listen too and learn from about this shtuff. Now, when I have a problem, I actually test & test again to prove the part is bad before buying/installing a new one.

[@SteveRobReviews]

Hey Matt I'm looking into the secondary air injection on the ws6. Another place to look. If the check valve for one bank did not seal it would in fact cause O2 to be injected into a exhaust manifold P0171. A leaky valve code should set , "should". I could see how ECM would be confused .

[@shupola]

I noticed at 20:44 the chosen parameter for bank 2 was LTFT AVERAGE as indicated in the upper left corner while bank 1 was just LTFT. Also at 24:03 both bank 1 and 2 were on LTFT AVERAGE and were slow to respond to the induced rich condition. Without having watched the rest of the series, It seems the chosen parameters could be the reason bank 2 LTFT seemed to not respond as quickly as bank 1.

[@richardmartini9784]

Yo Dude.. I own trucks/ cars...Have to learn more to save more... I ~listen~ to your video's Every night All night/ til morning.. Keep up the Good work.. I am learning...It is sinking in.. Thanks. Good to see that even A smart guys like you can get stumped.. Now lets get it done~.. I will be Listening in and Learning Every night till i got it down......Your A.O.K Brother...

[@mkuehn5450]

trying not to jump ahead in the series, 15:33 "normal oxygen sensor response" shows both banks climbing to high o2 voltage, rich, with additive to fuel trims (frames 280 to 295)? setting aside throttle enrichment (quick change in tps) trims should only adjust for the opposite o2 values. short = brief, minor change, long = larger, slower change.

[@jdean399]

Great videos,cant wait to find out the problem, would an exhaust gas emission test help to clarify your lean code? Carry on with your videos!

[@spelunkerd]

I think it may be time to ask the techs at Autoenginuity to drop by here and offer advice. I have noticed that substituted values and open loop activity is a little hard to recognize on Autoenginuity. It seems the enhanced readings are not accurate, but that could be from miscommunication between the PCM and Autoenginuity. If it's just a scan tool communication problem then it would be hard to justify the expense of PCM work. Whatever the problem may be, we need to explain the trouble code that triggered all of these investigations. I like your decision to reset the PCM by disconnecting bat neg, and restarting with fresh data.

[@SchrodingersBox]

Yes Dave but I have a new idea- As you said there is much variability in whether I am using enhanced vs generic parameters and which ones can be "trusted". In one mode I would be chasing evidence of a vacuum leak. In another mode- evidence of a fuel deficit. So I will be validating the scantool results with independent electrical measurements to determine which it actually is.

[@wtbm123]

be interesting if the same code gets set , if so freeze frame data , may show what was out of line to set. I know people have told me generic is more real time but never put that much thought in it till now . I will have to start comparing the data on cars now .

[@SchrodingersBox]

Yes this dramatically changes how I will do things using my scan tool in the future knowing this can happen!

[@techsavantlove]

One more thing. Paul Danner did a video where he showed that a vehicle saw "bad" or "no" readings from an O2 on one bank, and started using the O2 signal from the other bank as a substitue. I believe it was on a Ford pickup or a Ford car, but I'm not positive. If I find that video, I'll let you know. So, according to him, it IS possible for a PCM to run with one signal, and plug it IN TO BOTH CHANNELS on the PCM (as opposed to running with one good signal and totally ignore any results from the other sensor). That's probably clear as mud.

[@SchrodingersBox]

Oh I would love to see that video- that would explain everything except that I was able to create a definitive change in bank 2 by pulling a bank 2 injector connector. Were the O2 being borrowed from bank 1, it wouldn't have noticed that.

[@AutoFocus-se]

I will wait for the next part for sure.I need to know how this turns out and I like the activity in the comments. I just want to add, or ask, if you have loop status on the scan tool. I have read that it can show, on some cars if it have a loop fault.

[@georgeheri895]

Matt, I also se autoenginuity, and for some reason on certain model gm autos once a code appears even if in the pending file the data becomes inaccurate. your on thee right track resetting every thing. I had an issue with a 2000 buick with a bad map sensor, once the code appeared in the pending file ,no engine lite yet the data was no longer accurate. everything seemed to work normal data wise meanwhile the car was running terrible.

[@Bobbygale121]

Happy to see I'm not the only one who gets his butt kicked ....

[@jefferybryan5981]

It took 3 weekends but I found the vacuum leak (MAP hose just beyond the elbow but facing down). THANK YOU .....NO PARTS just a little electrical tape. Solid Schrodingers.

[@SteveRobReviews]

Fantastic - scan tool failure last on my list. ECM second last. All scan data as you know is processed data and only displays what it sees from sensor data. If at any time sensor data is illogical so will displayed data be shown . To me this is a classic case of bad sensor input. I would look at input sensor data pids only and I think you will find an illogical input. Freeze frame data , don't think it was shown. I'm shaking my head as well but I think the resolve will be simple . I have ran into scan data that showed illogical data between generic and enhanced and every time it was a bad sensor input. Wish I knew which one but that would spoil the test. 😊

[@SchrodingersBox]

Steve Rob FreezeFrame was shown in part 1- and it showed B1 LTFT at 24 and B2 at about .8 so go figure lol!!! But that was under load while driving which I have not reproduced yet in generic mode. Steve, I can't thank you enough for being the first to make the comment on substituted values that broke the case. I will not forget that!!! I will defintiely be re-examining sensor input based on your recommendation, however do you not agree given the responses in Generic mode- sensor inputs (at least as far as for fuel trim) seem accurate?

[@SteveRobReviews]

I agree completely but I did observe an illogical display between generic and enhanced thus an anomaly occurred between the two and this is what we look for. Normally you should not see a difference between modes under normal conditions . The data seems to show a completely uncommon condition. The car runs great no drivability concerns so without the mil on you would have never known the difference, thus what are we chasing a real lean condition or not. Is the lean condition a hard fault, substituted values can only apply during a hard fault. Erase the code does it reappear immediately or does it need to meet a certain criteria to set and the clue is at that point. I would look at the injector pulse widths as the trims go positive proving fuel is being added . We may have to perform an exercizim :)

[@TheWicklunds25]

So, when our OBD-II vehicles have faulty or damaged sensor inputs and they make unilateral decisions in real time based upon a set algorithmic response? What's the algorithm? I mean, if we're talking logic and mathematics it should be predetermined unless there is no substitution of data going on.

[@SchrodingersBox]

Great question. See my video on "fuel cell mapping: and it explains all that. Be advised though- it's not exactly a relaxing fun video to view hahahaha. Lots of math!

[@TheWicklunds25]

Question: How does the pcm estimate a value of a non-responsive input? Is it because it knows the stoichiometric calculation to make the STFT go to zero?

[@SchrodingersBox]

It uses what is known as a "substitute value"- that is a value that even if the input is missing, this fixed default value will be used to still get the engine by with reasonable performance.

[@MrAveGuy]

Disconnect the battery to reset the PCM. Maybe the PCM has gotten itself loaded with bad stored/learned data.

[@adrianapollyon5087]

Battery unconnected for 2 weeks (due to waiting for replacement parts on bmw) made the door lock and other computer generated objects work properly again.

[@johndecowski8007]

If you do have a vacuum leak I wonder what the enhanced data will look like after you repair the leak. Is this a data problem you've always had and never noticed? That would be interesting. For enhanced side I wonder if there is a software glitch that are malfunctioning under just these conditions.

[@SchrodingersBox]

This is definitely not a problem I had all along but never noticed- Everything I have learned about engine diagnostics over the past 6 years was done using this exact scantool (autotap) on this car and believe me- the car has always responded predictably and correctly to the variables I introduced over many years while teaching myself this stuff. In fact, a recent video I did several months ago also confirmed LTFT responses in both banks. Until your comment in Part4, I have never used generic data before- ever. The only two possibilities I can think of are a recent communication failure has developed with my PCM in enhanced mode only OR a recent communication failure has developed in enhanced mode on both my scantools ONLY on my car (since the scantools worked fine in ehanced mode on other cars as recently as yesterday). You know what I have to think is most likely.

[@Sandbag1300]

Schrodingers Box Why not test the hypothesis that in your vehicle the issue of bank two LTFT non-movement is driven only by specific codes. Let's assume scan tool generic data is drawn directly from the main trim tables in the PCM unadulterated and scan tool enhanced data is drawn from tables in the PCM that actually control fuel delivery to the vehicle. Those fuel trim tables could be the main tables or default tables that exist to protect the engine from run-away fuel trims - like limp home tables. When that specific lean code is triggered in your vehicle lets assume that the PCM of that vehicle is programmed to begin pulling fuel trim codes from a separate default table that does not vary as much to sensor conditions to protect the engine until the condition is fixed. Once those active and pending codes are cleared from the PCM the PCM programming will return to pulling fuel trim codes from the main tables. You are now testing this for episode 6. Very exciting!

[@johndecowski8007]

I agree with Steve. Every single car that I've ever put a pcm in that didn't need one, ended being an input reading somewhere that was off. I always smacked my forehead after putting the pcm in and then later "after finding out the pcm didn't fix it" found a input that was causing the problem. I now am very very cautious and will spend more time checking every possible input with s magnifying glass. Also what codes are in the generic side? A lot of times you can have different codes. I usually will check both. Maybe there's a clue there. Very exciting look forward to knowing the outcome!

[@SchrodingersBox]

Absolutely correct John- I have only ever seen one car that needed a PCM. Shorted injector that shorted out the driver in the PCM- fuel signal was constant at all times directly from the PCM (wish I had a video of it- it was awesome seeing raw fuel literally pool under the exhaust pipe under a cloud of white smoke that looked like a head gasket). There is also too much variability for this to be a bad PCM i believe. The computer is trying to make up for something that's missing. But no codes since resetting them. Just really high LTFT. Also- inside information- i'm working on the next video and no vacuum leaks

[@billyr9840]

Hi Matt, When you get a chance, take a look at my last couple posts. Last Night I was half asleep and gave you some misleading if not wrong info! Sorry, No Throat Punches , Please! Really, I went back and edited them to correct my errors, and I really think some of the info will be useful to you in understanding the purpose and operation of that GM .450 mv Bias Voltage and the PCM's monitoring of the O2's Heater, and Heater Circuits. Can't wait to see what surprises you have for us in the upcoming vids! Thanks for the Heads UP!

[@michaelmillion183]

I noticed in enhanced mode you could display LTFT Average and just LTFT in the Auto Enginuity scantool. Is there a difference? Forgive me if this was already brought to your attention. I haven't had a chance to read all the comments yet.

[@SchrodingersBox]

No this was not but I am interested only in the actual real time LTFT since I am inducing several variables to intentionally see immediate reaction.

[@techsavantlove]

When using AutoEngenuity, you used propane to go "rich". But you did not do a "lean" test by opening a vacuum hose. I would think that would be worth doing. Also, here is a postulation for yourself and the more knowledgeable experts to think about. I'm sure somebody will know the answer to this> The question is: Assume that the air/fuel ratio is such that all the oxygen is being fully burned (or as close as is possible in any engine). Maybe it could be a little rich, even. THEN, when you add propane, would you still get a noticeable rpm change? Or a change in the O2 readings? My sense about propane is that it is usually used only when there is suspicion of a lean condition, I haven't heard of it being used to test a good stoich, or a rich condition. I worked on a car that had a vacuum leak that did not give very significant results when using propane, but gave excellent test results when using carb cleaner. In other words, and I don't know combustion chemistry enough to know the answer, but if ALL the oxygen is being "used up", what effect would propane have? Do the O2's respond to pure unburned propane? Do they see that as rich? Does propane itself contain a meaningful amount of oxygen? If the engine is already at good stoich, or even running rich, would all the propane burn up? Is raw unburned propane seen as hydrocarbons? Or would only BURNED propane be seen as HC's? I assume you don't have a 4 gas anlyzer, but it would be fascinating to use one with this Case Study. Maybe you could borrow one? I really think you need to repeat the testing that you did with AE, but do some vacuum introduction tests. The first test, just pulling a hose. Second test, pull a hose THEN add propane. Third test, pull a hose and add carb cleaner. Also, if you are putting the propane into the end of the intake snorkel, maybe it would be worth trying to feed it in much closed to the intake manifold, maybe using a vacuum hose that would be somewhere around the thottle body area. It would be easy to shoot a stream of carb cleaner into a small vacuum hose. Be careful of intake backfires though. Also, I encourage you to use a can of carb cleaner, and go all around the edges of the intake, everyplace you can get access to. I know some people might think using carb cleaner is "hazardous", but I don't think it is any more hazardous than propane. I have had very good luck using carb cleaner. The thin plastic straw lets you really get to small specific closely targeted areas. Also, and I don't remember if your car has a MAF, but assuming it does, make sure that the propane you add is WELL PAST, and WELL AWAY from the MAF port and the sensor hot wire element. If any of the propane geoes through the hot wire port, the engine will see elevated air volume, which will screw up your test results, creating less reliability (I THINK). Every thing I have written here could be completely wrong, so don't be too hard on me. I don't own any Haynes manuals. Also, I don't remeber, and don't have time right now to go back and watch the previous 4 parts (I will later), but did you already use a smoke machine? If not, maybe we're gettting close to the point where it would be worth doing, looking in particular at the manifold, but other areas as well? The whole "generic codes versus enhanced codes is pretty interesting. When everything is totally fixed, I think you should go back and do A/B testing of the two scanner programs. Also, I have not read the comments on this page, and have not read most of the comments on the other pages in this series. So some of my thoughts might have already been expressed. Thanks The result of all this work will be fascinating, assuming you do eventually find the "answer".

[@xploringdnature6074]

My car is running lean bank 2 when I scan it,but no engine light showing. What do you think is the problem? Thanks for the help in advance.

[@SchrodingersBox]

What data do you have?

[@xploringdnature6074]

@@SchrodingersBox I would like insert the video but I can't to show you the live data.

[@SchrodingersBox]

@@xploringdnature6074 No need- just give the me the relevant data and especially the total trim curved against load. Keep it basic!

[@xploringdnature6074]

@@SchrodingersBox I'm not Mechanics so I will try my best to read the live data. SHRTFT1 15- 16 LONGFT1 7.8 SHRFT2 18.8-19 LONGFT2 9.3 SHRFT12 13.3 GO UP IN DOWN 15.6 SHRTFT22 16.2GO UP IN DOWN 21.20 O2S22 0.095 GO UP IN DOWN 0.600 O2S11(MA) -0.008 GO UP IN DOWN -0.051 O2S12 0.105 GO UP IN DOWN 0.725 02S21(MA) -0.008 GO UP IN DOWN -0.086 I hope this will help? Thank you for your patience.. Merry christmas!!

[@SchrodingersBox]

@@xploringdnature6074 Thanks but I need to fuel trims curved against RPM to tell anything. There is no way to say anything given that dataset

[@bryandavis341]

Do you have the base version of Auto Ingenuity or have you upgraded the software? I want to get this software but don't know if base software will be adequate. Thanks for your videos I took learned alot.

[@SchrodingersBox]

Base version.

[@bryandavis341]

Thanks. I appreciate your help.

[@bryandavis341]

Schrodingers Box Thanks for your help. Keep up the good work.

[@abdullbasitosman5070]

two questions: 1- 2003 toyota camry 3.3 v6 trouble codes p0171,p0174 , at idle stft b1 is normal ltft 42% stft b2 reach to 18 % ltft b2 49% . at 1000 or 1500 5pm ltft b1 b2 go down to 14% stft b2 stuck on 18 or less . when i drive the car at constant speed 12 mph stft of both banks change to negative ( close to -14 or 12 ) . is it fuel regulator at tank? 2- assume fuel pressure gauge needle bounce ( right and left) while engine is at idle does this mean at least one injector is dirty( doesn't spray enough). ?

[@SchrodingersBox]

abdullbasit osman 1. No 2. it could but also could be dozens of other things.

[@abdullbasitosman5070]

what those dozens? fuel pump? if fuel pump is weak fuel pressure gauge will read below thee specific value but in case of dirty fuel injector and good fuel pump gauge will read normal but needle bounces ( less and normal less and normal ) ,if fuel pump is weak + dirty fuel injector the fuel pressure reading will be below and needle bounce below the normal value . do you agree me? assume normal value= 55 psi dirty injector and goof pump needle bounces 55 and 50 .for example . dirty injector and weak pump needle bounces 50 and 45 for example . sorry for my bad English and asking much .

[@TexasPLNR]

Your use of Autoengenuity on another dual bank car to locate an intake leak increases liklihood of internal firmware fault in your PCM. Your fear of PCM replacement is unwarranted. They are readily available and very inexpensive from salvage yards. You may run into some complications w/ matching your old keys to new PCM or need new keys matched by a locksmith. I eagerly await further installments. This is better than a Hercule Poirot mystery!

[@SchrodingersBox]

You are absolutely correct Tex, you have seen me use enhanced PIDs in other videos- in fact EVERY other video! Until now I have never used generic- why would I? I sure know now lol! I agree PCM's are easily available at salvage yards but not for this car. You will never find a LS1 engine at a salvage yard- only V6's. But I am familiar with the security issues in changing a PCM and know my way around it. If I establish I need a PCM then I will certainly look into it but I haven't tried resetting the computer yet. But yes- given the only constant is my PCM not communicating in enhanced mode with two validated scantools- it's hard to think of any other explanation ain't it!

[@wtbm123]

To bad don`t have a Exhaust Gas Analyzer. To independently see if either bank is actually lean. ,Well just a thought

[@SchrodingersBox]

Thats actually a great idea. I wish I had an oscilloscope too- basically anything that I can use to validate what's real vs what's not real here.

[@techsavantlove]

This link: Ford O2 Sensor Testing should take you to the link danner did, where he show's a PCM on a Ford Taurus 1998 adopting the signal from ONE O2 to run the fuel trims on the OTHER bank (both banks running off the signal from just one bank). This IS NOT a Substituted value, as such. In other words, it is not a fixed value from one cell. The PCM appears to be adjusting the trims on both banks using the O2 information from only one sensor, after it decides the data from one sensor is bogus. Also, he was getting a Ford Enhanced Lean Code P1131 (but not an 0171). I think the ONLY code you were getting on your Trans Am was JUST the 171. I have looked for a full list of all Pontiac or GM Enhanced codes for year 2000, or a full list for all years, and haven't found it. However, this comes close: service.gm.com/gmspo/mode6/2000eparms.html On that page, scroll down to the "5.7 LS1 / G F Camaro / Firebird", and you'll get a link to a PDF document that is a list that is probably pretty similar to what the list for a TransAm would be. There aren't really any Lean codes as such, just some O2 switching time codes, listed toward the bottom of the document. In other words, I was looking for an Enhanced Mode code in the GM world that would be similar to the P01131 that Paul had on the Ford Taurus.

[@b4322558]

hey matt i mite have a bad ecm with my 2000 chevy 1500 5.3 yesterday I was driving it and didn't reset the check eng light and look at my dash just for it and saw the check eng light off and have saw this before ......so know I need to find a vido at checking the ecm with this p0171 p0174 lean codes

[@billyr9840]

Matt, Sorry to bother you again, but I can't stop thinking about this dam car. Starting to feel like it is my car! After reviewing all of these vids in this case study again several times. I am more confused then ever. In part 5 when you pulled the injector on B1, you said there was an immediate response by the O2 sensor for B1. But when I reviewed the film, after you pulled the injector, and right before your batteries went dead ( I wanted to punch you in the throat! LOL!) I did see a response of the green trace for LTFTs and STFTs to go positive and the green trace for the O2s go negative. Then the film cut out. Here's where I am confused, I thought the green trace were from B2 but you said you pulled a B1 injector. Please, Please, rectify my confusing, I'm ready to throw a concrete block through the windshield of the first Trans Am I See! LOL!

[@SchrodingersBox]

Billy R Hahaha, you and me both. Don't worry- I have new video that will have plenty of study with unplugging the sensors and looking at the effect on the other bank. I may have mis-spoke in last video but either way wait til you see the next video when I examine this further... it only gets worse bro.

[@billyr9840]

Schrodingers Box NOTE: I edited this post because when I originally posted it was 4:00 AM up here in CT and I was half asleep! The way I described the procedure and I talked about a bias voltage being sent by the PCM. The test I was thinking about is the same but it is for a three wire sensor such as a TPS. the results are the same as far as substituted values go, except that you can use this bias voltage to check the integrity of your signal wire. The PCM sends a 5 volt bias voltage on the signal wire to the TPS through a very high resistance and current limiting resistor from the PCMs 5 volt ref. The PCM uses this bias voltage to monitor integrity of the TPS circuit and associated wiring. You can use this test to check the integrity of the Sensor signal wire and the 5 volt REF wire too! By back probing the sensor with KOEO, at idle, you should see about .75 mv on the signal wire. If you unplug the signal wire from the sensor, the signal wire ( Not the 5 Volt Ref wire ) should rise to 5 volts and this shows that your signal wire from the Sensor back to the PCM is good. If it does not then you have a shorted signal wire to ground and your reading will be close to 0 Volts or your 5 Volt Ref. Signal is shorted to ground. Not all three wire Sensors have this Bias voltage but an easy way to tell is to see what the sensor signal wire reads plugged in then unplugged, if it rises when unplugged than it has a Bias Signal! Note: I Corrected my errors in the rest of this post! I believe! It Gets Worse! You Mis-Spoke! You really do want a throat punch! LOL! No all shit aside, it was kind of funny to hear you stumble, but hey dude what you are doing, and they way you are doing it, Gotta salute Ya! Sounds like its bugging the POO-POO out of you too! After reading your post, sounds like you've been burning the midnight oil doing some serious experimenting. Speaking of experimenting, Got a good experiment for ya, to help you comprehend that substituted value stuff. Hook up your Scan Tool in Generic/Global mode, Get your DVM out and back probe signal wire of the IAT or the ECT with the KOEO at room temperature. You should see around 2.5 to 3 Volts. the PCM is interpreting that voltage as around 60 - 70 degrees F. Now unplug the sensor ( which ever one you chose ) and you should see that voltage rise to close to 5 Volts on the signal wire and -40 degrees on the Scan Tool. ( If the voltage rose to 5v you just confirmed that your signal wire is good from the sensor back to the PCM and is operating properly, if id did not or you had 0 Volts then you have a short to ground on the sensor signal wire. The 5 volts on Signal wire is being sent from the PCM through the PCM's 5 Volt Regulator ( Not the 5 volt REF Signal ). The PCM is going to interpret that 5 volts as -40 degrees in it's built in lookup tables. Now change the Scan Tool from Generic/Global mode to Enhanced/OEM mode and read the sensor output ( Temperature ) on the Scan Tool. The reading you are looking at is the PCMs substituted value that it implemented when it detected the loss of the ETC Sensor Signal so the car will run somewhat decent so you can get home when a sensor like that malfunctions. ( Limp Mode). Note: The PCM might need a RPM signal so you might need the engine running. I'm not sure if Substituted Values is part of are problem or not, but as a general rule of thumb, if you see some values that are strange or seem to be conflicting with each other, you should run your Scan Tool in Generic/Global OBD 2 mode because, by Federal law, the engineers that write the programing for OBD 2 are mandated by the EPA ( www.epa.gov/obd/ ) not to include Substituted Values in the Generic/Global Format. Thank God, for Steve Robs suggestion of Substituted values! The man wasn't sleeping at the wheel! To be honest, I knew about them before hand, It just never occurred to me to think of it or that you were in Enhanced/OEM mode. Let me know how you make out if you decide to try my little experiment.

[@SchrodingersBox]

Well I'd love to know why in generic mode if I unplug either O2 sensor it shows the O2 sensor voltage as .45V.

[@billyr9840]

What does it show in Enhanced?

[@billyr9840]

Matt, to answer question, that is the PCM sending a bias voltage to the O2! How many wires are on your sensor?

[@mikeb5981]

I’ve heard bad gas or low gas in gas tank can cause lean conditions. Idk know true it is, I’ll find out myself tomorrow

[@SchrodingersBox]

it’s absolutely false. if there is enough gas to pump its enough

[@mikeb5981]

@@SchrodingersBox I’m talking about bad gas, if a vehicle has been sitting awhile with gas in it. You don’t think bad gas could cause lean conditions?

[@SchrodingersBox]

maybe if it sat 15 years. bad gas is almost entirely a myth. When a person cant figure out what’s wrong- “must be bad gas”. This is usually conclusion after changing plugs, wires fuel filter snd O2 sensors. It’s an excuse, not a diagnosis.

[@techsavantlove]

ENHANCED MODE GM codes: I went to this page at AutoEngenuity: www.autoenginuity.com/images/vehicle_samples/GM/GM-All-Systems-List.html It gives a VERY MASSIVE list of what I believe are ALL of the Enhanced Mode Signals and Sensors that the Enhanced AE package can talk to or read. It is a massive list, and obviously would not all be supported on any given vehicle. In fact, I'm sure you'll agree, a lot of it would only apply to cars much newer than your TA. BUT, there are a LOT of fascinating sounding Commands, Signals, and Sensors listed, including a whole mess of Oxygen Sensor stuff. There are also a dozen or two Codes or Cammans (or tests?) regarding the PCM. Pretty interesting. Have you used AE to try to "interrogate" your PCM, to do any "self-testing", etc.? Not that I think any of this info, or any of the info mentioned in the previous post are going to be of any use to you here. Just passing on what I found.

[@jaberwocky6669]

I always understood generic PIDs to be the universal set of all implemented PIDs amongst all manufacturers. The enhanced PIDs were the manufacturer specific PIDs for which expensive modules would need to be purchased to read. Am I wrong on this? And If this is not wrong then how could enabling enhanced PIDs cause any sort of weird substitution or whatever it is? Oh just replace, the pcm, os sensors, plugs, wires, coils, and oil pressure switch. I KID! I KID!

[@icggeneric7836]

Did you clear ECU memory after O2 swap ?

[@SchrodingersBox]

Yes

[@techsavantlove]

SOFTWARE: I've been thinking about the comments made by you and some of the more advanced subscribers, regarding the PCM, AE, and how they are "talking". I'm certainly no software expert, BUT......... It is POSSIBLE (I'm not saying this is or is not the case, only that it's possible) that there could be a software code "glitch" in AE, OR there could be said glitch in the programming of the PCM, OR in BOTH. In the software world, it is totally not unusual for any given operating system (I'm a Macintosh Systems expert, no real PC knowledge), to have a glitch that only shows itself when using a specific software program, sometimes only a specific VERSION of one program, with ONE particular version of the operating system. Example: Say you have Mac OS 10.4.11 This was a very popular and stable version that was used by millions of people/computers for years. Now suppose you were using Adobe Photoshop version 7.0 4. (just making that one up, I don't remeber the Photoshop versions exactl)y. Now, it is very possible that there could be ONE Command or Function in Photoshop that would only occur quite rarely, depending on what you were doing. Maybe you were trying to run a Filter, on a particular format of image file. But every time you tried to run THAT ONE FILTER, and never when doing anything else, the program would lock up, or the O.S. would lock up. As I say, this is just a totally made up example. I've seen many things similar to that in my career as a Mac Systems Administrator, and later as an independent Mac Systems Consultant. So what's the point, I hear you say. Well, the point is, that MAYBE there is some very bizarre, "one off" flaw in either AE, OR in the GM PCM code, that is causing the weird "Global it works/Enhanced it doesn't" thing. And even MAYBE it is a COMBINATION of the two. Some little flawed line of code in the PCM software, AND some little flawed line of code in the PCM software, neither of which would ever cause a problem unless you were trying to do one very specific task, such as reading LTFT in Enhanced Mode on a particular Engine/PCM combination. I don't know what an LS1 is, I assume it is some kind of high performance engine that GM put in some TransAms. NO scanner software engineer, no matter how good, can test every single function on every single bit and byte of data that their program will see on every single variation of vehicle that the program might be used on. It's truly impossible. Every software application of any size that has ever been released has flaws. They are just so minor that very often they are only discovered by a few users. And there is always the chance that a few lines of PCM code don't adhere very well to "suggested" standards from the SAE. Of course, everything I've said will probably turn out to be irrelevant and you'll probably have some very bizarre, even intermittent, vacuum leak. Opp's, make that VACUME leak. Carry on, and keep us informed. We are all biting our fingernails in anticipation of a resolution in this Sherlock Holmes worthy tale of intrigue

[@billyr9840]

I agree with your thinking, but I was thinking along the lines of when Matt booted up the software did it update its self. I've seen other scan tools do that and create a flaw or take away options that you had before. Your thinking sounds more likely do to it seams to be vehicle specific and only LTFTs, but who knows at this point!

[@jefferybryan5981]

BTW................STFT & LTFT numbers reading correctly. Thx again.

[@DJDevon3]

Who in the hell suggested either or both of the O2 sensors are bad. Did they even watch part 4 at all? That wasn't even worth re-hashing the explanation of the reasoning because you just did an entire video on it. If you want to argue that one or both O2 sensors are still bad after all of that please go watch Scotty Kilmer videos because only he would validate your asinine assumptions by telling you to buy 2 new O2 sensors.

[@billyr9840]

Don't judge to harshly to fast, remember you are looking at processed data from the pcm. The oscillations on the O2s you are looking at are very dependent on the communication speed of your pcm data link, scan software, and your pc and all of them have different transfer rates. Not to mention, the data is being presented as mv per frames in the software which on your average refresh rate of a generic scan tool is only about 10 frames per second per pid (halve that for every extra pid you add). If Matt had an oscilloscope that data would be presented as mv per ms. Then you would be able to see the actual switch time cycles of the O2s witch should be under 100 ms (100 thousandth's) of a second.

[@DJDevon3]

Billy R The chances of that are highly unlikely having seen the data streams from 2 different scan tools in 2 different modes.

[@fivefortyeye540i]

Under load more evidence..Not a vacuum leak.. Further rule out o2 looking at voltage swing? Maybe when you unplugged o2 u got that substitute value??.. Man I don't know! Can't forget about injecter 7,it lives in hostile environment??.. Man I would go back to the very beginning forget about fuel trims and look at o2 voltage swing.. Lean condition if not fuel delivery has to be the pcm! Man if this my car it drive me crazy.. Lol man I would be up wii hrs of the morning trying to figure out wtf!!

[@fivefortyeye540i]

I wonder what freeze frame data looked when code was set?? Did anything stand out??

[@SchrodingersBox]

fivefortyeye540i Freeze Frame was shown in Part 1 and it was bank-1 specific lean at +24 B1 and about +.8 Bank 2 while under load.

[@emmanuelmunozbass]

Schrodingers Box If you looked at the Freeze Frame data again but this time under generic. Do you think it would show the same?

[@SchrodingersBox]

Emmanuel Muñoz Yes- the freezeframe data would be the same because it is independent of the scantool- it is strictly generated and stored by the PCM

[@emmanuelmunozbass]

Schrodingers Box But in the end you're seeing it through your scan tool, just the same way you do with live data. What if that data is being misinterpreted too? Entirely changing the diagnosis... Would it hurt if you tried on your next video? (just for the sake of experimenting) Regards from Mexico! =)

[@SchrodingersBox]

Emmanuel Muñoz I will do that if I get another check engine light- but I can't get it to come on again!

[@02lowrider62]

You will find that once the computer is reset the enhanced data will work the way you expected it . Then I am sure you will find problem very quickly, I am sure its not a computer. Good luck

[@antiekeradio]

Weird stuff! I just found time to watch pt 2 to 5 so i'm quite curious as to what it turns out to be...

[@jamalmarafi4076]

maybe the o2 sensor has been changed .

[@SchrodingersBox]

why would that explain this data output???

[@pablomarquez4431]

Boy can engine performance be a mother....

[@abdullbasitosman5070]

how to know returnees fuel regulator is faulty ?

[@SchrodingersBox]

abdullbasit osman You would have to measure rail pressure and see that fuel pressure reaction is not as expected and indicative of the regulator.

[@jnarez1]

How about leaving one o2 out of the exh.

[@SchrodingersBox]

Yes in retrospect I should have done that instead of unplugging it. But I actually have a better idea... you'll see

[@mtrltoolman]

am waiting for pt6 .

[@SchrodingersBox]

Me too lol! This weekend for sure.

[@mtrltoolman]

hahaha

[@apollomedia7210]

Matt, I see that you are in favor of people being scientific and investigative. But you will also understand that flat rate mechanics are not rewarded for being through on their job. They are being rewarded for the amount of cars they "fixed". So I think we both understand why they are replacing parts and and spending as little time as possible on diagnosis. There is also the lack of knowledge and professionalism but that is another issue.

[@SchrodingersBox]

Oh I totally agree. And as my hobby has grown and I have become more in demand I have started to experience some of the pressures of time restrictions- I used to work on maybe 3 cars a month. Now it’s 6 cars every weekend. Indeed I have had to modify my protocols to accommodate for the fact there is seldom time to be 100% conclusive. However I still do this on videos for the educational value.

[@jcsaves9725]

Damn, generic codes, wow.

[@fivefortyeye540i]

Something is lying! You got 3 choices.. 02 sensors, scan data, or the wrx pcm.. Bottom line!

[@ahill007ny]

Hey Matt ScannerDanner did a video on substituted values you should see, granted it's about a GM MAF, he explains substituted values, and how he almost replaced a PCM. kzbin.info/www/bejne/e5nHn5menrmca7c

[@Mr032789oscar]

This is live data at iddle on my 2005 corolla. Fuel trim:99.2 Throttle:16.1 Maf:1.8 g/s Engine load:14.5% Codes are: P0171 P0102 P0113 The fuel trim does not change when i accelerate. I dont know where to start without fuel trim changing and being so high. Any way yall can help will be greatly appreciated.

[@SchrodingersBox]

oscar gutierrez Look at O2 sensor response and see if you have a dead O2 sensor

[@Mr032789oscar]

Schrodingers Box my o2 sensor seems like it is acting strange. It doesnt really oscillate. When it is cold it goes to .1 flatline. When i start accelerating it goes towards the middle. Then when it warms up it goes all the way to .9 flatline.

[@SchrodingersBox]

oscar gutierrez You need to induce rich and lean variables to validate if there is response.

[@Mr032789oscar]

Schrodingers Box so i went and took my car for a ride and when i parked and check live data the fuel trim never changed at 99.2 and o2 stayed at .75. I disconnected the brake booster hose to induce the o2 to go lean and it did all the way down to .1 Im so confuse to why my fuel trim is so darn high. And never changes position.

[@SchrodingersBox]

and what was fuel pressure at idle va load?

[@billygtrr34]

wow! sounds like a woman! it says something but really mean something way different

[@schrodingersboxquantummeka2008]

+billygtrr34 Hahahaha- well at least given enough time I am sure I can figure out the car though lol

[@techsavantlove]

See: www.motor.com/article.asp?article_ID=1356