Test Your Lean P0171 / P0174 Diagnostic Skills-Pt6

Here I rule out mechanical problems that may be causing lean conditions with a slew of tests, and in the process find more variables depending on my scantool mode being in generic or enhanced!
Part 7 is here: • Test Your Lean P0171 /...

[@ДаворДабић]

One of the primary benefits of the generic datastream stems from the requirement that it not display substituted values. While many so-called enhanced interfaces offer access to a greater number of data PIDs, some of these may reflect substituted values not based on current operating data.

[@spelunkerd]

One knock I have about Autoenginuity is that they don't offer a primer to explain these kind of things (generic vs enhanced). I guess they assume that anybody who buys this software would know, but I didn't. When data comes up as a substituted value I think the program should show a red flag, and I think open loop vs closed loop should be immediately identifiable.

[@atomicdmt8763]

and/also: critical to check the ground wire for your O2 sensors! I just had a breakthru after (hundreds of hours) of trying everything.. and then realized the ground wire in the circuit had a very corroded connection.. throwing off the sensors........ reading LEAN and therefore sending too much fuel to compensate...... fouling up the sensors et al. Once I snipped and corroded wire and made a solid GND connection, the P0174 code that kept popping up has gone away.

[@atomicdmt8763]

part 66...... derp! excellent info, great video. THanks!

[@ElectronicWorkshop]

great series of videos, not sure where the problem is yet, but im sure you will get there in the end

[@mkuehn5450]

another rule, I am NOT smarter then the engineers. blocking the clean air intake to the valve cover is a hard NO. it reduces the pcv flow, which in many cases is only a fixed orifice. i've had a couple customer concerns of the car "whistling" both while running, and after the motor is STOPPED. air leaking past crank seals from high crankcase vacuum was the root, and would continue after the car was shut off until the pressure equalized. BMW's have a spec for max vacuum at the oil fill, due to the oil separator (pcv) failing, causing fuel trim codes.

[@shaishavshah5114]

As far as i know in computation and programming, substitution is used when you don't wanna let your system shutdown for small reason and that thing involves substritutung the values implicitly rather then explicitly, i mean when u can't get the data from real world then u may have a way of predicting it and using it in ur algorithms...

[@steventenney8797]

Enhanced is great for egr data and desired values. The newer the car the more data on generic is displayed.

[@Giorobot]

Am eager to see the outcome for this you are going to put it together I know that but even if you don't still you show us lots of ways things don't work other words parts no to change

[@shaishavshah5114]

I don't know exactly the stuffs in car' pcm but couldn't we reprogram this PCM ?.. i mean the manufacturer must ha e these program backed up and they could reprogram the chip before we discard it ..m just throwing this from my automation experience...sorry for Guess

[@pablomarquez4431]

Maybe try using a basic scan tool with live data instead of the laptop at times to confirm faults.

[@12vgs8606]

I know it is lot of work but is it possible to merge the PC output inside the video stream via editor? It is extremely difficult to read the screen. I do not know if the scanner gives you .mp4 or some time of video file. I believe ScannerDanner does do merge of his scope data right inside the youtube video.

[@SchrodingersBox]

12vgs8606 Yes I can do that but it's a lot of work. However I will be doung that when I get my upgrades for video and processing soon.

[@mcconn746]

It appears this series is complete so my comment is irrelevant. Let me also say that I had never heard of fuel trim before a week ago and it was from one of your videos. I, however, am a retired Quality Engineer and have significant gauge experience. With that said, is it possible you have low voltage going to your PCM...possibly a corroded power connection. I once had inconsistent engine issues caused by low voltage on my outboard.

[@SchrodingersBox]

Low voltage to which sensor?

[@mcconn746]

@@SchrodingersBox Sorry I did not make clear. I was speaking of low voltage to power the PCM which from my outboard experience can cause erratic running issues. My outboard would actually stop a few minutes and then run like a champ over choppy water. One of the battery terminals was a little loose so I would think choppy water would not allow it to run well. I was just wondering if corrosion to the power terminal of the PCM could cause erratic behavior. If so, someone could replace the PCM which would at least partially clean the terminal and the issue would go away. Again, I am a novice and just trying to learn. Thanks for all your work.

[@SchrodingersBox]

That can't be possible in this case- we see full voltage from the power sourcing to all components while they are under load.

[@mcconn746]

@@SchrodingersBox Thanks. Obviously that covers it. I am a novice. I was not aware you could confirm full voltage to all circuits under load at one time. I will continue watching your videos. I really appreciate your work and will likely sign up for your premium channel.

[@oscaralarcon6695]

There is a short in the electrical wires which may be causing the wires to have weird troubleshooting.

[@SchrodingersBox]

+Oscar Alarcon What????

[@peteraazar9442]

@schrodingers box your right scannerdanner is the man. Must make a lot of money

[@justinle998]

What is the difference between enhanced and generic mode? And what are substituted values?

[@SchrodingersBox]

Enhanced mode allows far more parameters to be read while generic mode allows only mostly the same basic parameters required to be available from all OBD2 vehicles. For example, generic will read the same parameters on most cars such as O2 voltage, map, maf, fuel trims, etc. Enhanced will read that and up to hundreds of data that may be specific to the vehicle like cylinder misfire, IAC position vs desired position, engine load% etc. Often the enhanced data is extrapolated from generic data. In the event a generic input is not available (say the IAT is not connected) The PCM may use "substituted values" to fill in the missing information to just get by. For example if the IAT is unplugged, it may be better to use a value of 75degrees than to use zero. If you saw 75 degrees on the scan tool when that is nowhere near the actual IAT, that could be a substituted value- just something the PCM defaults to when real data is unavailable. Sometimes substituted data can be calculated by the PCM from other sensors. For example if the MAP was disconnected, by using the TPS, IAT, and MAF, the PCM can gave a pretty good idea what the MAP should read and may plug in that estimate if MAP data is needed for any reason,

[@justinle998]

Thanks for the quick response. Best repair channel on youtube!!

[@bartscave]

The brake booster won’t show smoke due to the check valve.

[@SteveRobReviews]

Is there an aftermarket performance program installed into the pcm . Oscilloscope oh yeah makes a difference especially on the maf. A stretch but verify there is not excessive AC voltage from the alternator. Danner is watching for sure and I bet he has a very good idea what's going on , might be he's just observing to see if his youtube students can figure this out. I believe your logically eliminating possible faults. Unless you have experienced this you would be doing exactly as shown. I would recheck MAP - TPS - MAF one more time to be sure.

[@SchrodingersBox]

Yes it has an aftermarket programming however I reverted to default programming for this case study- and there was absolutely no difference anyway. The car has had vacuum leaks before in the years I owned it- and even a stuck open AIR checkvalve all detected and repairs verified by using AutoTap and reverting the anamolous LTFT's back to zero on both banks- now I only read one bank. I agree with your idea on the MAF but unfortunately I have no way to test that- yet. I'm looking into oscilloscopes. I also noticed my Bias voltage read at the O2 wire is only .37V, not .45V like scantool shows- but it is same on B1 and B2. Fishing too deep maybe?

[@SteveRobReviews]

Bingo - that's interesting as long as the 02 was stone cold. .450 mv I believe is the correct spec. Your unable to test the 02 for required 3 cross counts in one sec. as normal ? The 02 seem to have good amplitude but frequency you can not test with a dmm. Scan tool look for around 140 or more grams per second w/ o throttle on the maf. I'm leaning to the maf still as for the sub/values wow this is wild. Pcm power and grounds , I'm not $1000.00 Pcm sure yet, don't even want to go there. LOL . If we don't fix this by the weekend I suggest you call Paul if he's not too busy,great guy always willing to help those willing to help themselves . A view from another prospective would be helpful .

[@billyr9840]

Schrodingers Box Matt, Read my posts ( Not sure which one it was, but it was when I explained the .450 mv Bias voltage ) in Part 5 and you will understand why you are seeing .37 mv when you check O2 signal wire with your DVM

[@billyr9840]

Billy R Matt, Since you don't have an Oscilloscope you need to test to see if the computer is responding correctly to the O2 outputs. An easy way to do this is touch the positive side of the battery with one hand, and touch the O2 signal wire with your other and see if the Computer responds to this. It should go up well in excess of one volt. It is completely safe. to the computer. By doing this you will be sending 12 volts to the PCM, but your body has such a high resistance to current flow that that it will not harm the PCM. Current flow creates heat and that is what would burn up the voltage/current sensing circuit in the PCM. You could even use a test light connected to battery positive, because your bulb in the test light has considerable resistance as well. Most people are scared to, so use your fingers.By doing this test you are confirming the PCM is capable of reacting to the O2 outputs. You already proved that the PCM is monitoring the O2s by unplugging the O2s and seeing that .450 Bias Voltage. You may have to wet your fingers because your outer layers of skin are so dry that they do not conduct electricity very well at so low voltages. And if anybody doubts that, take a 9 volt battery and stick it on your tongue! These two test alone with good results would make me lean away from PCM issues. Last of all I did not like seeing them voltages exceeding 1 volt when you were back probing the O2s. Remember your DVM reads an average of voltages so how high were they really?

[@SchrodingersBox]

Billy R Yeah exactly what I was thinking, as far as average o2 voltages being higher than 1.5V. I was advised by subscriber "Electronic Workshop" to try using the frame as ground and seeing what the values are. I agree that given my misunderstanding at the time about unintentionally inducing OL-3 as a result of my efforts to determine computer response to B2 inputs, I did not actually succeed in my efforts and will consider your advice to confirm independent bank responses to O2's but I have some other ideas too.

[@jcsaves9725]

Really hope it was not the pcm! What I’m going through is not the same but similar.

[@shaishavshah5114]

I always afraid of letting my car fall in to the hands of part changers...hahha...but there is no way of trusting somebody untill u spend something on them..

[@fivefortyeye540i]

What is actual maf g/s at idle??

[@geraldmartin3625]

Just curious, what did you have written on your can of MAF cleaner? All I could read was only.

[@SchrodingersBox]

Hmmmmmm, Let me see.... it says: "MAF Cleaner".

[@geraldmartin3625]

+Schrodingers Box I meant what you wrote on the can. A warning note to self?

[@SchrodingersBox]

Oh that lol- it’s just says “use of MAF only”. It’s because it’s fricken $8 a can!!!

[@jamalmarafi4076]

on may scan tool it I've got this reading open in heated oxygen sense B1S1 circuit low resistant in heated oxygen sensor H2O2 bank 1 sensor 1 circuit measured across sensor , failed engine control module [ECM ] .. 1

[@SchrodingersBox]

test continuity of heater circuit.

[@12vgs8606]

No, there is no separate pin on ALDL for enhanced communication.

[@SchrodingersBox]

12vgs8606 Thanks Bro, I think I got the lean condition solved, but the enhanced parameter thing still a problem. New video coming soon....

[@SteveRobReviews]

Most GM cars produced in 1996-2003 use J1850-VPW interface. Check your using the correct mode for enhanced. glad to gee the lean is resolved- Seafoam ? LOL

[@SchrodingersBox]

Steve Rob Seafoam- really? lol

[@DavidGomez-gl1oc]

STEVE R OB

[@jpack61108]

Eric O from SMA is pretty good too. Just saying :)

[@SchrodingersBox]

Oh indeed he is.

[@rohanboswell5408]

by looking at the comments from of these people i am so amazed that so many people have no clue about diagnostic,i would tell you to stop posting , but i realize , a lot of people really have no clue

[@emmanuelmunozbass]

Hi Matt, I just bought an oscilloscope about 10 days ago and I couldn't be any happier. I was able to diagnose a bad timing setup when my engine was rebuilt on my 97 jeep cherokee. (I was able to pick up the cam and crank sensor signals flawlessly.) Here's the URL and it only costed me 68 bucks! www.amazon.com/gp/product/B00FYGEFYM/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1#product-description-

[@12vgs8606]

Never knew such a thing existed! Can you hook it up to an Android tablet instead of a laptop?

[@emmanuelmunozbass]

Unfortunately no. The software that comes with it uses the .NET framework. So, it even has to be a laptop running with windows...

[@wtbm123]

Watching

[@jasonargone5993]

Everyone I know has a enhanced scan tool, lol, toss a set of wires and plugs at $50.00, save a few hundred bucks of ' ingenious diagnostics',