Understanding Short Term and Long Term Fuel Trim (a SD Premium video)

Рет қаралды 504,519

Күн бұрын

This is a ScannerDanner Premium video recorded during my class at Rosedale Technical College. The rest of this series on oxygen sensors and fuel trim can be found here.
• Chapter 4 Oxygen Senso...
Engine Performance Diagnostics chapter 4 pages 7-19
Topics cover
- purpose of short term and long term fuel trim
- which fuel trim data is retained in memory
- upstream and downstream oxygen sensors
- purpose of bank control fuel trim
- how to use fuel trim to identify type of lean condition
- how to tell if the fuel trim has reached it's limit
- counter fuel trim number (did you fix the car?)
- what does a vacuum leak look like compared to a low fuel pressure or dirty MAF sensor problem?
- how to clear long term fuel trim memory
Playlist
- (Chapters 4 and 5) Fuel Trim and Oxygen Sensor Testing
• (Chapters 4 and 5) Fue...
Related videos
- How to identify a vacuum leak using fuel trim data - 2004 Ford Explorer • P0506 IAC System RPM b...
- Low fuel pressure causing a P0171 and P0174 trouble code
• Low fuel pressure caus...
- Ford F-150 P0171 P0174 Trouble Codes - vacuum leak (water test) • Ford F-150 P0171 P0174...
- STFT reads opposite of LTFT (after repair fuel trim data)
• STFT reads opposite of...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC.

Пікірлер: 649

@TonyWadkins 11 жыл бұрын

I came back to refresh my knowledge on fuel trims and I don't think there is a clearer explanation on youtube. You are an incredible teacher! Thanks for sharing your knowledge!

@georgerodriguez5726 Жыл бұрын

+can't see shit

@Caradonia 11 жыл бұрын

It never ceases to amaze me why people like you go out their way to share so much of their knowledge and help people in the way you do. Thank you for your wisdom my friend, it's very much appreciated! :-)

@JoeSpivey2 Жыл бұрын

47 years in this business, I'm a tuner, a very experienced technician, and I'm at least a hundred training courses in on engine management. This course is an excellent training course in the operation of the fuel trim system. I actually didn't learn new things but again, nobody is born with this knowledge. I'm sending my technicians a link to this video because I cannot see into their heads and know exactly how much of an understanding that they have about this subject. I liked the way that Dan stayed away from brand differences, particular engine differences, and other variables and concentrated solely on the fuel trim system in general. Great job! I highly appreciate you giving this knowledge to bring technicians up to speed on these systems that have been in place for over thirty years and are in use on almost every vehicle on the road today.

@ScannerDanner Жыл бұрын

Thanks so much Joe! I have an entire training course available for next to nothing on my website too if your interested. It's perfect for any of your techs that are really motivated to learn this trade and it is full of timeless fundamentals. Oh, my name is Paul Danner btw 😉 My students gave me that name way before KZfaq because I always have a scanner in my hands www.scannerdanner.com/join-scannerdanner-premium.html

@combatjm89 6 жыл бұрын

This video has finally gotten fuel trims through my thick head. Thanks!

@dans_Learning_Curve 2 жыл бұрын

That's why I came here! Posting this at the beginning of the video.

@rayhindle642 9 жыл бұрын

Scanner Danner you make your lectures so interesting, wish my lecturers had been like you when I was at college, had to watch fuel trims two or three times before I could grasp it though, not your fault I'm nearly 64. Ray from the UK.

@electronmarkboggess63 7 жыл бұрын

I came out of heavy diesel and construction equipment repair and decided to go into automotive..much of the principles are the same but I wanted to become more familiar with automotive drivability diagnostics...I started watching your channel and bought your book and you really know how to put things into perspective. just from watching your channel and studying your book it helped a lot and let me take what I already knew as it pertained to 15L cat diesels and apply with to the automotive industry..great stuff man thanks a lot

@Airman.. 8 жыл бұрын

you are a real asset of KZfaq's community Danner, thank you for inspiring all of us Auto Mechanics to continue the job with knowledge and confidence

@ScannerDanner 8 жыл бұрын

+BahrainAirman thank you my friend

@NetSecNow 10 жыл бұрын

ScannerDanner You really do an amazing job. I myself am Master ASE Certified, and as we all know sometimes we neglect to K.I.S.S, which was my case today with a 98 Saturn 1.9l. Came in, no check engine light, rough idle, bad gas mileage, etc. STFT was @ -25% to -30% and LTFT was @ +9.4%. Realizing it was running rich based on the STFT values, I went ahead and pulled the booster vacuum hose to create an artificial LEAN condition. STFT didn't change, nor did LTFT. I thought, hmm. I checked Fuel Press, spark, etc. O2 upstream was moving accordingly high/low, so I was scratching my head for a bit. I watched this video as a refresher, and as soon as you said "reset the ECM for a relearn" that little light bulb went off, and the "DOH" moment arose. I did exactly that and a 3 key cycle test drive for a relearn, and bingo, my values are now back in spec. Looks like the previous shop replaced the vacuum booster line, and neglected to clear and relearn. Keep up the great work man!

@DENicholsAutoBravado 9 жыл бұрын

That's the 4th example in 3 days that I've run into. After the repair, do a reset. Some cars refuse to learn after they detect a problem.

@joshua8171 8 жыл бұрын

+NetSecNow Wow i wish all my repairs were that easy! Reset the ECU. Lol!

@kirkwest6654 5 жыл бұрын

Hands down best technician online period. Thanks for the hard work and dedication for helping others. Im 25 working for police departments fleet in MS almost 2 years in(mostly maintainace and not a whole lot of diagnosis) and im taking online classes. Hopefully one day I'll be half as good as you. First step is to keep watching your videos

@tommyscully4775 Жыл бұрын

@ScannerDanner 12 жыл бұрын

great suggestion, I'll put it on my list of things to do for sure. I'm working on releasing the entire book in this format. It will be over 50 hours of material. I'll keep everyone posted when it is done.

@JHoover8984 10 жыл бұрын

That's what I leaned in school anyway. Awesome video. I've spent hours watching your videos. Truly the best automotive series on the net. Keep up the good work!

@scottbolger4428 5 жыл бұрын

@scannerdanner my wife and I both have older vehicles that I maintain and fix myself. Your videos are incredibly helpful to me in my constant battle to turn the check engine lights off for vehicle inspections. Just wanted to say thank you.

@ScannerDanner 12 жыл бұрын

Thank you for your kind words. It means a lot. Paul

@KLM817 9 жыл бұрын

Thank you for this explanation. I have listened to a few techs try to explain fuel trim to me, but this by far has made the most sense. Thanks again!

@djrocker1007 7 жыл бұрын

Best demonstration explaining fuel trim I have seen. Great job! Thank you

@orangekitties44 4 жыл бұрын

ScannerDanner, You are the man! you help the do it yourself community in diagnostics! no words to thank you enough

@ScannerDanner 12 жыл бұрын

Thank you very much for the comment and book purchase! And I will keep the videos coming.

@ScannerDanner 12 жыл бұрын

no problem joe and thank you very much for the kind words

@miyu7i 8 жыл бұрын

Sir, thank you so much. In such a nice way you explained everything.. I really appreciate your efforts.. Cheers..

@ScannerDanner 8 жыл бұрын

Thanks for watching!

@miltonscornertobylove5068 9 жыл бұрын

Man do I want to get my hands on verus scanner, God bless you. You do a good job training ur students, wished I had an instructor like you in my days lol 👍👍👍👍✌

@fivefortyeye540i 12 жыл бұрын

Finally! a entail comprehensive tutorial on the subject of fuel trim.. Thanks! Dan for bringing clarification to this subject..

@mitchellheadington5182 7 жыл бұрын

Wow this is one of the best videos on how internal combustion engines work i have ever seen. This was extremely well explained and helpful, thank you.

@ScannerDanner 7 жыл бұрын

Thank you!

@ScannerDanner 12 жыл бұрын

thanks for your very kind words.

@ScannerDanner 12 жыл бұрын

That's great man, thank you. You will not be disappointed

@tsant6591 11 ай бұрын

Here we are 10 years later, to reference this well taught, valuable information. Thank you!

@ScannerDanner 11 ай бұрын

Thanks man! 10 years later is awesome

@jrivas356 12 жыл бұрын

Scanner Dan you are the man! I'm 21, just got both my Verus certifications not to long ago and am about to graduate with an associate in Automotive Technology. Excellent lecture! I got more out of your lecture on ST/LTFT than I did with both my basic and advanced Fuel Systems class! Love it when you use the Verus as well as incorporating real world problems and fixes into your videos. If only every automotive teacher had the intellectual knowledge you brind to the drawing board. (pun intended:)

@thesmartguy3523 Жыл бұрын

Dang man, this video is 10+ years old, how far have you come brother ? I'm sure you've now become a master tech ;)

@SS-U23 5 жыл бұрын

Great explanation and I will watch it at least one more time. thank you

@Maverickf22flyer 3 жыл бұрын

The most thorough video explanations upon this subject. Thank you very much bro!

@kazadimowambad 12 жыл бұрын

this is the best delivery of fuel trim explanation i have seen . big ups...

@huracan200173 12 жыл бұрын

ScannerDanner, I must say IMHO you're an excellent teacher. You teach the theory, then show it in the field with expected outcomes which helps the student to reason what he has been told. Not only that, you ask questions along the way to see if the students are understanding what are you saying. Someone could say it's pretty obvious what I'm saying, but I've known A LOT of teachers that lack this kind of pedagogical way of teaching.Not only that, you're showing all of this by free. THANKS!!!

@muddydisco4 11 жыл бұрын

Excellent informative lesson, I learned a huge amount.Thank you very much for taking the time to explain something that I struggled to understand before.

@nigelstringfellow5187 3 жыл бұрын

Now I understand !Thanks Paul for everything you do .Cheers

@ScannerDanner 12 жыл бұрын

Agree with your approach completely as far as waiting on the cat. code. Check the PCV hose under the intake for a crack. This is very common on the 2.0 engines, not sure about the 1.6. I have seen also on Fords the stem area of the EGR worn out. When I changed my EGR on my explorer I had a 10% improvement in my LTFT. They all leak a little in this area though. Even the new ones.

@ScannerDanner 12 жыл бұрын

Thank you very much! Something to consider in the future thanks.

@ScannerDanner 11 жыл бұрын

thank you! i am glad it made sense.

@ScannerDanner 12 жыл бұрын

Thank you very much! Hope you are satisfied with it so far. Let me know.

@miclewis55 11 жыл бұрын

Brilliant presentation .... many thanks for the upload ... fantastic insight into the overall strategy of the ECM and how the fuel trims report it's adjustments.

@mikechiodetti6737 5 жыл бұрын

THAT WAS an EXCELLENT Theory of Operation followed by actual test of a vacuum leak, then an extra fuel injestion (not injection) and how the system can self correct. What you said about having LTFT positive 30% and STFT-30% can be confusing, but showing +30 and subtract (-)30 = "0". It becomes a little more simple at that point. Then it's up to the system to self correct, or delete the codes and wipe clean the fuel trim memory, then observe it with the engine running. WOW!

@hayksamvelyan 10 жыл бұрын

Wow what an excellent video on Fuel Trim data. I'm trying to diagnose my own car issue, as the car has a very nasty smell on cold starts, and this is helping me a lot. Thank you ScannerDanner.

@eurowerx4267 2 жыл бұрын

You the man! Appreciate you sharing your knowledge to the community💯🙌🏻

@plunky1000 11 жыл бұрын

hey this class was awsome all my year being a tech this is the first time i understand fuel trim thanks man

@user-pw8yu7nd7p 5 жыл бұрын

A great thank you from Greece for the education we are given

@2Phast4Rocket 8 жыл бұрын

Wow, this is a great video. I understand a lot more about the fuel trim and the relationship to the O2 sensor.

@BENDPAK7000 12 жыл бұрын

You have wisdom beyond your years, SD.

@mac1mike 2 жыл бұрын

22 years wrenching. I can finally say I understand it.

@ScannerDanner 2 жыл бұрын

Awesome!!

@dznuttzonyachin7499 2 жыл бұрын

I got me a BlueDriver just for basic stuff. And I'm starting with fuel trim graphs. Slowly gonna learn that module then buy a more expensive one. Thanks for your videos !! You guys are awesome !!

@ozzstars_cars 11 жыл бұрын

Excellent explanation. My short term and long term memory thank you!

@MrLuvallcars 7 жыл бұрын

Respect. Great effort, excellent explanation and demonstration. Much appreciated!

@JTSAMPSON04 6 жыл бұрын

You do such a great job explaining this. I own a 2008 Toyota Camry 4cyl With no problems until it developed the fabled oil consumption problem. It didn't throw any codes... just burned one quart oil per thousand miles. Well, to Toyota's credit they wrote me and told me to bring it in because they had identified that model was having that problem. I had gone to the dealer and they had pleaded ignorance. Long story short, they replaced all four of my cylinders. 5 miles after leaving the dealer's service facility the car through a PO171 code and acted like it was coughing up blood. I hurried back to the dealer's but they had closed. Had to drive the car over the weekend and it got better and better.... But the PO171 code stayed. Well the dealer at their own expense replaced the intake head gasket, checked the fuel pressure, said they found a crack in the PCV hose, added a can of 44K and finally put in a A/F sensor (at my expense) based on a P2238 code. None of these worked to stop the PO171 code. Additionally, soon after occasionally the car developed a condition in which it would not start after being driven about 20 miles and if I would stop it would not start. On these occasions I found if I waited 20 minutes or so the car would start. However, it would start if I sprayed some starter fluid in the intake. That was three visits to the dealer at their expense and they could not find the problem. Otherwise the car drives fine. So I'm left with trying to find a problem myself or as they said wait until it just want start. I have waited a year. I have looked at your and other videos, Google articles, etc. I have changed spark plugs, air filter and checked for air box leaks. The car is too good to be just junked even though it has 280,000 miles. After all it is a Toyota. I have had no problems with it until the oil problem. It has stumped the dealer and me. But, I am trying to diagnose some things. I bought a scanner. I am not mechanic. Bought a generic live data/1 parameter graphing scanner out of desperation because dealer could not find the problem. At idle....the scanner said; 2008 Toyota 4cyl 2.4 LXE @ 900 RPM right after start up 122 degrees F coolant temp STFT -3.1% LTFT +35 to 44% IAT 57 degrees MAF ???? CLoop except when snapped WOT the trottle when it temp went to OLoop After driving 10 miles: 670 RPM in idle CLoop 201 degrees F STFT +4.7 to +10.2% LTFT +34.4 to 44.5 % IAT 113 MAF .32 5.02 (very varyable) O2SB1S1 -0.01 ma Cat Te11 635 degrees F Cat Te12 341 F LAMBDA B1S1 1.000 BARO 30 (never varies a lick from this) At this point I cut it off. Again it would not start!!! Tried starter fluid still no start. Waited 20 or 30 minutes started up without the starter fluid. Acts just like an old car I had with a vapor lock problem.

@rubenbebanco3734 5 жыл бұрын

thank you paul great video... evry tme i watch this video i learn somthing music to my ears

@shanusav 6 жыл бұрын

Incredibly well explained. Thanks

@4wdaddict41 7 жыл бұрын

thanks man everything you post is alot of help

@ScannerDanner 12 жыл бұрын

Any time, thank you

@Sloppyjalopy123 6 жыл бұрын

Great content, the best video I've seen so far on fuel trims. I'm trying to learn how to tune fuel maps using fuel trims. This was very helpful.

@ScannerDanner 6 жыл бұрын

Thank you so much!

@waynehutchinson1423 3 жыл бұрын

Thank you,l have watched a few vids on this fuel trim issue and couldn't grasp the concepts of lean means rich and rich means lean and how the computer manages the 14.7 to 1 ratio and reading a scan tool correctly.This was great!!!

@ScannerDanner 3 жыл бұрын

Thank you! "Command" is opposite of "condition" if that makes sense.

@ScannerDanner 12 жыл бұрын

Nice, glad you liked it.

@spelunkerd 12 жыл бұрын

Yeah, I got the electronic edition of your book last week. It makes a big difference when you have the background and fundamentals.

@fieroboom 3 жыл бұрын

Absolute TREASURE TROVE of information!! 😁👍👌

@alb12345672 12 жыл бұрын

This is a GREAT VIDEO. I reset my KAM and watched my car learn its LTFTs at idle with my scan tool. Sometimes the vac leaks though can be very difficult to find or expensive to fix. I just fixed a nasty one around a leaking IMRC end using a RTV and a nickel. I went from 20LTFT to 6. I know the other side is probably leaking but its not worth bothering!

@joeg2727 6 жыл бұрын

Thanks, for doin this, you explained a few things i didnt know. Your doin excellent work.

@shasheekaushalya4253 10 ай бұрын

WOW... The amount of information in your videos are off the roof sir!! well done.

@ScannerDanner 10 ай бұрын

Glad you like them! Thank you!

@ruenjou 6 ай бұрын

Explained very well and I liked the real time demo. Thanks

@michaelstoltz58 9 жыл бұрын

I just want you to know that I learned a lot from your videos in the past 6 months. Swore off mechanics years ago, and haven't touched a car in 15 years. Bought a beater of a KIA sportage for $1000 that somebody basically beat up, and threw away. Leaves inside the valve cover. Failed smog twice. Bought unnecessary parts for it,and then found the secret hidden vacuum port, and plugged it. Bought an OBD ll scanner, and watched a gang of your educational videos, and have been able to diagnose, and monitor the vehicle. STFT modulates at both 0.8 and 1.6 on both sides, and the LTFT is at 2.3. Idles great, and performs really good. Thank you Scanner Danner. (Think I'll make a smoker just for fun).

@geraldmartin3625 5 жыл бұрын

Thank you for sharing your knowledge. Your book is on my wish list.

@Pyroethics 6 жыл бұрын

This is prolly the longest video ive watch in youtube with no regrets. Love the contents you put up!!! Keep up the great work.

@ScannerDanner 6 жыл бұрын

Thanks man. Hope this helped

@MrMotofreak72 8 жыл бұрын

Great stuff Paul! This was very easy to follow so thanks

@elgiro15 11 жыл бұрын

Thanks for taking the time to response, I live in NY so probably the fuel can in fact be an issue but in the past years we have try changing to better fuel grade and didn't see any good result. But I will give this another try since now I have a few devices to read live data from the car.Car has the IAT build into the MAF sensor according to the reading seems to be ok this past few days I get reading like 60 F as I start driving and engine get hot it get to about 96-114 F..continue....

@calvarycoffee 12 жыл бұрын

Thank you for making your lectures available here. Please keep them coming! It's great to find college level training videos I can watch on my own time, and not have to pay a hefty tuition fee. Looking forward to purchasing your book(s). :)

@256emmitt 11 жыл бұрын

Paul... Your knowledge of engine diagnostics has been very helpful to me. Earlier today I bought a scan tool that gives me more comprehensive diagnosis. And I've discovered about fuel trim issues which has determined of my engine running too lean. Just to give an example of the fuel trim readings. Long term is reading between 20 - 25%. And the short term is reading at 15 - 20%. Not to mention the idle is a bit rough. Anyway, I just want to give you thumbs up.

@ScannerDanner 11 жыл бұрын

thank you!

@pabloarevalodelaguila8767 4 жыл бұрын

Excelente explicación, ahora si entendí completamente los ajustes de combustible, y eso que tengo que traducir el video para poder entenderte. Gracias.

@user-uj1xg7hb2u 2 ай бұрын

Experience Gained, Thanks Forever Danner❤

@ScannerDanner 12 жыл бұрын

That is correct my friend

@sikupnfed 2 жыл бұрын

Thank you so much. 10 years later and today I saw the light. I will now attempt to solve a reoccurring P0430 on my Toyodor. Feed the cat. I like it.

@gearhead7961 8 жыл бұрын

Thank you so much for this lesson, I will definitely use this information.

@sunjoomoontube 2 жыл бұрын

Rocked my brain. Deep thanks.

@mikes6388 9 жыл бұрын

I bought your book recently and this video made a few things very clear. Great stuff!

@ScannerDanner 9 жыл бұрын

Thank you!

@ScannerDanner 10 жыл бұрын

Thank you!

@martinsmartinsautobodyandr6740 Жыл бұрын

I let your channel play on a large flat screen TV in my collision repair shop and so many people actually watch and pay attention to your videos and say I never realized how some of the computer stuff works in a car.

@ScannerDanner Жыл бұрын

That's a great idea! Awesome, thank you!

@VictexPilot 10 жыл бұрын

Excellent video and teacher. Thank you very much.

@iulixxx 12 жыл бұрын

I can't thank you enough for this videos.

@sivucit 12 жыл бұрын

Mind blowing video. I have learned this before and paid a LOT in dollars to learn all this. I bought ur book very useful and ur videos are much useful. The difference between you and other is, you teach the theory and show how that theory can be used in real life, where as other i can see too much on thoery and very less or nothing on practical. You are great. Adding another point, even though i learned this theory from other, i always learn new things when you teach. Great.

@ScannerDanner 12 жыл бұрын

Thank you

@nadeemahmed640 4 жыл бұрын

Thanks sir appreciate your efforts.I am from Kuwait and i always watch your videos .

@evanriverrat9232 3 жыл бұрын

Dude you Rock. God Bless you.

@ScannerDanner 12 жыл бұрын

Cool man, thanks for the update. Definitely sounds like a vacuum leak with improved fuel trim numbers at higher RPMs

@kevinanglin678 3 жыл бұрын

My long term shows -30% short term is 0-3% has misfires on all cylinders also what would cause that big of a number on the long term?

@ScannerDanner 3 жыл бұрын

@@kevinanglin678 -30% is a big problem. First thing to make sure the oxygen sensor is functional, then you'll need to find out why the engine is running so rich

@rickwest2818 5 жыл бұрын

Excellent explanation, easy to follow.

@ScannerDanner 11 жыл бұрын

+/- 10% And yes on your exhaust leak question.

@StreetBikeTakeoverYT 10 жыл бұрын

thanks you soo much man !, I didn't get confused throughout the whole video whatsoever.. awesome job explaining :))

@erikarevalo1874 3 жыл бұрын

@ScannerDanner thank you to the fullest💯

@ScannerDanner 12 жыл бұрын

Go to my website listed in all of my videos or on my youtube channel page. I cannot post a link in here but search Auto Computers Troubleshooting d o t c o m (no spaces, all small letter). Fill out your name and email in the comments box and I will send you out some more info. about the ebook. Thanks!!

@auttomotiveelectronicperfo2010 10 ай бұрын

Amazing teaching technic as well awesome knowledge! Greatings from Brazil!

@SteveRobReviews 12 жыл бұрын

Well done !! lean and rich apply to both the O2 as well as the amount of fuel confusing for some people. A lot of people think the O2 reads amount of fuel and not oxygen. I help out at an auto parts store and lots of customers buy O2 sensors because the scan tool says so and it's normal for them to come back and say the sensor we sold were defective because the light is still on. I try to explain O2 readings to customers as a rich oxygen level or a lean oxygen level.

@v-modsolutions6946 5 жыл бұрын

Flipping great info! At 55 years old, retired law inforcement, would love to be in your class!

@roro560v8 12 жыл бұрын

Thanks for the informative video, Just now I understand what's going on , I am gonna kick some asses in my school ....THANKS YOU ARE THE MAN Keep it up