Expert Techniques in Advanced Vehicle Diagnostics: Part 2

[@bernardocisneros4402]

Oh man! Great video with a lot of good information. It took me 1 hour and a half to absorb all this good info. I had to pause the video to listen to some parts more than once, and read some of the slides. Great channel. I just subscribed and rang the bell for future notifications. Please keep them coming.

[@electron-john]

Thank you for watching! As long as you are willing to watch, I will keep making videos!

[@fastestcaskets5020]

I always preferred the classes you hosted on AVI over most of the other instructors. I am happy to have found your KZbin channel. You're an asset to the industry John, thank you for making quality training available to everyone.

[@electron-john]

thank you so much for the kind words! I kind of miss the technical training and that is why I started trying to do these KZbin videos as often as I am in town.

[@djosbun]

Fantastic video, John!

[@electron-john]

Thank you

[@AnthonyHart-jd5nm]

MAN!!!! You are absolutely brilliant describing the OBD/Communication system's! The T.C Motor Control/TCCM went bad in a 2000 Chevy Blazer! Its been 2 months of research, cause and effect... the list goes on. It's been 2 months and finally ready to fire after watching 2 or 3 hours from your teaching. Your techniques tied scattered thought, unfinished research, and ignorance together beautifully! The, Ability, Knowledge, and Art Form when describing the correlation between the System Algorithm/Mechanical Functions, are second to none from here, my opinion. Thank you, Sir!

[@electron-john]

thank you for the kind words

[@anthonyrosa4388]

the way you EXPLAIN everthing is as if your drawing it in my head. THANK YOU!!!!!!🤯

[@electron-john]

thank you for the kind words! thank you for watching.

[@shakeelsss]

Just impossible not to watch your educational videos over and over due to the tons of critical informations. Always a pleasure.

[@electron-john]

thank you so much! now if only the rest of KZbin would feel the same way.🤣. should have the next video up by the end of the weekend🤞

[@Christopherbever]

This was one of the best explanations I have seen! Thank you for taking the time!

[@electron-john]

Thank you so much!

[@GripFreak]

Hi John, I must admit you're one of the best diagnosticians I have seen on YT. John Kelly is tops as well. Thanks for sharing your immense knowledge and experience. I plan on purchasing your book and some of your tools. One day I would like to attend your class.

[@electron-john]

I appreciate your time watching and commenting

[@rayp.454]

Thank you for explaining the details in layman terms. We are not all professional techs, but are happy to learn from an experienced teacher like yourself. Would like to see more videos like this John.

[@electron-john]

glad it was helpful and thank you for watching and supporting the channel

[@JesseAutoDiag]

Great video John.!!. Please continue to put out this type of contents. "Diagnostics using Scope"

[@electron-john]

thank you for watching and the next video is going to be about obd 2 and it’s 10 modes with a heavy emphasis on mode 6 , however I will soon be returning to scopes!

[@briansilva9120]

Hi John, great video and thanks for sharing all this great info. I’m following and looking forward to more videos like this in the near future. Keep them coming and keep up the great work. Thanks again 👍🏼

[@electron-john]

hi Brian, thank you for watching! thanks for the kind words as well. two more videos being added to the series shortly

[@s.j.5850]

Incredibly good video John! You had the wheels spinning in my head. Hard to find an expert in automotive electronics these days. Once you understand the concepts of voltage, current, resistance, & signals you can figure out where & how to proceed. You give us a lot of detail so that we can sift through what's relevant & what's not. Look forward to seeing your next video.

[@electron-john]

Appreciate that big time!! We work tirelessly to bring you the most in depth and real world knowledge and experience in each of our videos. Hearing positive feedback really gives us the drive to keep delivering on every release!

[@JOHNSUE28]

John, I have added you to my must watch list. Pine Hollow AD. South Main, Watch Wes Work. Your in very good Company. Thanks.

[@electron-john]

Thank you. I am both honored, and grateful

[@tonypybus8003]

I am an old school vehicle electrician - I broke my teeth on british military vehicles - Land Rovers, Bedford Trucks, Chieftain and centurion tanks (with he 27 liter v12 merlin engine which was used on the Spitfire and P51 Mustang) where the ignition system was a coil, a distributor, a set of points and number of high tension leads and plugs. The only sensors were an oil pressure and a water temperature sensor! Fault finding was really easy. It was the same on the cars of that era. I really enjoyed seeing how to troubleshoot modern cars. Thanks for your efforts - I look forward to seeing more insightful videos in the future - keep them coming

[@electron-john]

Thank you!

[@ThunderbirdRocket]

Nice one ! 👍🏼🔥

[@electron-john]

Thanks for the visit

[@bartscave]

Thanks John! Good information.

[@electron-john]

Thank you for watching

[@lupedelacruz4152]

Very good information Juan I subscribed and Will follow You now amigo thank you thank you thank you very much

[@electron-john]

Thank you for watching and taking the time to comment

[@keithbland5365]

Thank you for sharing your knowledge with us. Could your next video be about solenoids in the automotive world today? Which solenoids should be checked first if ECU has gone bad?

[@electron-john]

hi Keith, that’s a great suggestion and I will incorporate it into our future list of videos. thank you for your support!

[@cruze1953]

New subscriber here. Your channel is awesome! Looking forward to more Electron John. I cut my teeth on the Sun Scope and 4-gas analyzer in the 70's and 80's. We're probably the same vintage.

[@electron-john]

welcome , and glad you are here. we probably are the same age. lol

[@sheerwillsurvival2064]

Brilliant test for analog converters 😱 I have soooo much to learn

[@electron-john]

thank you for your support

[@windward2818]

For upstream HEGOs (narrow band, switching) closed loop fuel control, the strategy is a switching control (because the HEGO only detects two states, rich or lean) with a long time constant filter or a long time constant PI or PID control loop supplying learned fuel trim data, which is then used as a mean fuel bias level upon which the switching algorithm is optimized. If the learned fuel trims are correct for the current engine operating condition, the fuel switching algorithm will use a symmetrical jump back around stoichiometry, essentially trying to maximize the switching frequency. The upstream HEGO works well for this closed loop control because it is directly in the exhaust stream. The jump back (bang bang) control is not a controlled frequency as output, it will result in a set switching frequency if the fuel trims are perfect and the catalytic converter (CAT) operation optimal. The switching waveform is the result of everything in the control loop. The HEGO signal switching amplitude should not change pre and post CAT like shown in the drawing in the video if the two sensors are identical, and if the CAT was perfect the post HEGO would not switch at all (complete and efficient O2 control) or perhaps be pegged lean. In fact, the intermediate voltages (mid span) of the HEGO output between the normal rich lean switching thresholds are meaningless. So the CAT efficiency (or other such OEM words to describe CAT health, which is crude at best) makes sense only as a relative measure of the pre and post CAT HEGO switching characteristics. So, we can make inference between pre and post CAT switching but not amplitudes. For identical pre and post sensors the output should be the same, registering either rich or lean. This is where understanding the CAT monitor strategy OEM description is very important. Because it may imply that the CAT monitor is a special test pegging rich or lean at a certain point in the drive cycle to understand relative HEGO switching behavior. But, where in the drive cycle for emission would you intentionally control CAT breakthrough, ideally you wouldn't. This is why CAT OBD II monitor (test) is done over two complete drive cycles with specific operating conditions before the test is run. But, we could rephrase this and say the test is so crude that we don't want to set a DTC unless either the CAT or HEGO is spent. To really see the HEGO outputs it is best to directly probe the signals at the HEGOs (use differential scope probes) and not plot scan tool data.

[@electron-john]

thank you for watching. your reply is full of a great deal of technical responses. I must admit certain things like bang bang and other I have never heard of in my tenure as an automotive technician or instructor. I would love to study/learn more of which you are speaking. do you have any trainings or videos you could share?

[@shakeelsss]

I have seen that test more than once. The first time was SMA then SD , I forgot the last one. They called it circuit test integrity.

[@electron-john]

Yes it can also be used to test the circuit proving the 5 volt reference wire and the signal return wires are in tact. The difference when viewing the waveform is to watch the pattern on the screen . It should stay steady at the reference voltage, if it starts to bounce up and down, that is the sign of an analog to digital converter going bad. Again, this test should be done if multiple analog type signals have generated a dtc

[@nowayjose596]

Why would a PCM be looking at (and adjusting for) a knock sensor during cranking? This is a known "noisy" time as you mentioned, and the end result would be it reducing ignition advance erroneously, no?

[@electron-john]

Great question and I am glad you asked. Basically we do not want added timing advance when cranking because it makes the engine have a hard time starting. The ignition occurs to much in front of the piston reaching tdc and since the rpm is low during that time, the engine struggles to overcome the the starter trying to fight the power stroke event. Not all vehicles will have this strategy but the ones that do will use an rpm sensor and see the cranking rpm is happening . It assumes this condition based on low rpm, say 2-400 and confirms its suspicions of cranking by seeing a noisy knock sensor due to , as you said, the starter gear meshing with the flywheel teeth. It also uses load sensor input to help confirm its suspicion.

[@nowayjose596]

@@electron-john Ah, ok, so if I'm understanding correctly then it's utilizing the knock sensor to arrive at the "correct" ignition timing for cranking/starting, not retarding it even further than desired like I originally thought. That's an interesting strategy rather than just programming in the (reduced) ignition advance you want during cranking and ignoring the knock sensor input during that time, but I guess it does give the PCM a way to tell that the starter motor is no longer engaged and increased timing is desirable when it stops hearing that noise? If you have an issue with an inoperative knock sensor in a system that uses this strategy can it lead to harder starting, or at least more current draw by the starter? I really appreciate you taking the time to respond to my earlier question (and making these videos in general). I'm in the automotive program at my local community college and having resources like this are immensely helpful, so thank you.

[@IamReadyToRock]

Excelente

[@electron-john]

thank you

[@bebeto71-iv4qq]

Hello,Sir. I know a maf sensor reading with key on does not matter. Should the reading fluctuate a lot? If not, what would cause this sensor signal to be erratic with just key on?

[@electron-john]

while it’s normal for the voltage at the sensor to drop ever so slightly while the hot wire warms up, it is not normal for it to fluctuate a lot as you stated. I would suspect either a wiring issue due to loose connection or unwanted resistance somewhere or even possible a battery issue since it is just key in engine off. do you happen to notice the headlights doing the same thing? if so, suspect a battery issue.

[@bebeto71-iv4qq]

@@electron-john I will check the headlights when I get to see the vehicle again. I checked other vehicles and the readings are stable. We have a different sensor that we can try.

[@georgebell3964]

👍

[@electron-john]

thanks for watching!

[@abhijeetsurve2226]

Hello sir I am Abhijit from India please suggest me automobile oscilloscope purchase - bandwidth min required please tell me sir

[@electron-john]

hi, thanks for your support. there are many great scopes on the market. my favorite high end scope is the Pico model 4425. mid range scope would be the autel, and lowest price would be the MT pro from joesautoelectric.net

[@luiscruz-no3ib]

I am sorry, John, but you made an incorrect statement. You said neg is lean .negative in the trim means rich it means is pulling fuel, not adding

[@djosbun]

John was talking about voltage at the sensor, so he is correct. He is not talking about ‘%’, which is how some people view fuel trims with their scan tool.

[@electron-john]

Hi Luis, where did I say this incorrectly at? I watched the video again and could not locate where I said it incorrectly. You are correct with your statement that anytime the fuel trim numbers are lean that is a result of rich exhaust and anytime they go rich, it is due to lean exhaust. I just couldn’t find where I said it incorrectly in the video so if you could point me to that section of the video, I would appreciate it!

[@luiscruz-no3ib]

Lean means too much oxygen, not voltage, which means an incomplete combustion wherever there's a near complete combustion, it is not going to be found oxygen

[@djosbun]

@@luiscruz-no3ib He’s talking about measuring voltage at the O2 sensor. Go watch it again. Low VOLTAGE at the O2 sensor means LEAN.

[@djosbun]

@@electron-john Hi John, you didn’t say it incorrectly.

[@charliemagoo7943]

A waste of time video. Had an ad for some fixd dongle the guy said it worked as good as his expensive scan tool.😅. Why do i as a technician need a scope when i could just use that miraculous dongle?????

[@electron-john]

Hi Charliemagoo7943, Thank you for responding, I am a little confused. I did not mention any dongle in this video. Maybe you saw an ad that youtube placed within the video? I do not control the ad placements. However, my goal is to share knowledge with other professional technicians, so if there is a type of content you feel would be beneficial, please let me know.

[@charliemagoo7943]

@@electron-john actually good video. The google ads were for dongles to fix cars. I honestly doubt anyone learning from your videos would buy the dongles. They are on different levels.

[@electron-john]

Thank you!@@charliemagoo7943

[@georgebell3964]

👍