Look old man, I’ve been a senior master ASE tech/mechanic for over 25 years, after listening to you going on and on about your diagnostic theory I feel the need to say…… thanks. I’m still learning. Just subscribed and I’ll be going through all your previous videos and checking in for new ones as well.
That was one of the most useful 20 minutes of my life! Amazing presentation both in terms of content and delivery style. You have a new subscriber.... (with a new Creader VIII diagnostic tool).... Thank you :-)
I have tried numerous times to explain this to rookies. I must say that I would not make a very good teacher. That is why I refer them all to either watch your videos or find out more info on their own. Believe me also that you can also teach an old dog new tricks. Thanks again, this is a great video. Keep them coming.
Great video. I learned it slightly different but, basically the same in that the computers response could be compared to an old style tv. The short term is like a fine tuning and the long term is like changing the channel when the fine tuning reaches its limit.
11:30 Thanks for this excellent video. I need some of your expert guidance. 2011 Hyundai Sante Fe engine failure126,000 connecting Rod bearing failed. Warranty engine installed by Hyundai. 6000 miles later engine lacks power. Finally I get a check engine code PO106 defective map sensor. Replace it with a OEM Hyundai map sensor . Check engine light goes off.No change in running condition . Vehicle is towed to the dealer Dealer. Dealer diagnosis, 2 defective CATS melted and coming apart inside. I claim the ECU was not communicating with new engine or updated when it was installed. We were probably driving vehicle for many miles with a faulty map sensor( making the engine run lean or rich) but the check engine light never came on and when it finally did it was to late the cats were compromised. My other reason the CATS failed is when the original engine blew up it sent engine parts ( rod bearing, connecting rod , piston and engine block)coolant, oil and fuel right into the CATS compromising them. It’s now a battle with the dealership trying to get them to replace the CATS under the engine warranty. Dealer checked the ecu with a basic scan And says its working. No check engine light currently on and no codes For catalytic converters . The dealer also ran a compression test 140,160,160,160. Not sure if this imbalance would affect the AFR in each cylinder? Any advice Appreciated Thank You
You just explained ,very simply and articaly what I have tryed to explain to young people I have worked with. Most of them and customers when you mention 02 sensor they think that it can't be causing there problems .Not to mention like you said you can go from a bad 02sensor or bad coil and end up with a destroyed catalytic converter all because of a simple problem and then the crying begins and how stupid what ever car company who built the car is .A car being worked on right now 2005 Mazda tribute . With 3 kats ,it started with a misfire to bad coils ,was driven quite awhile like that .Needless to say ran scan .short term and long term fuel trim1 all at 0 .and a open loop fault With all upstream 02 sensors. And a whole lot more .just by looking at every thing on the scan tool kats are blocked EGR tube and EGR blocked
There's only one feedback sensor and that's the old two sensor which really is amazing because it's measuring the oxygen or the heat coming out of the engine the heat is indication of the oxygen if that makes sense that's how they get a sense of reading is by the heat
Basically the whole sensors react to temperatures they just measured in a different way the old two sensor the oxygen sensor creates a voltage between .1 and .9 and this gets the computer the signal of the heat in the exhaust and we call it an oxygen sensor.
The fuel trim is showing you what the computer is doing to keep the engine running at efficiency if the computer is saying that you have more gas going in then that can mean you have a air leak in your intake system it's trying to balance it out so what's more critical is if the long-term fuel trim is not at 0 or neutral then you really have a big problem the short-term fuel trim should be going up or down a little bit to control the burn of the fuel which is pretty much measured by the heat of the O2 sensor and the heat of the O2 sensor which we call the oxygen in other words if you have a high signal you're not getting enough gas if you're getting a low signal you getting too much gas and you can imagine the O2 sensor only puts out a 0.9 volt to a 0.1 volt so you can imagine how close it monitors the heat of the exhaust gas coming out of the engine I would think you need an O2 sensor for each cylinder but it's happening so quick that you only need one per six or four cylinders or eight cylinders it depends on the manifold if you have 202 sensors they just last longer because you have two manifolds exhaust manifolds
Hey. Superb video. I have strange problem with short fuel trims. My engine is BMW M54B30. On bank 1 i got +25-28%, but on bank 2 it is ok 0 to 5%. I know that my oxygen sensor after cat on bank1 is dead. Is this can affect on fuel trims? MAF is working, I checked rubber hoses and there is no cracks. Help please. Thanks.
If your not sure how rich (or lean) the ratio is, would unplugging the MAF sensor be a way to reduce harm to the cat? Would it bring it back to default mix? I've just had a new cat fitted today, yet now see a prior 'too rich' code and a Maf voltage too low code. So am now concerned that the new cat will burn out fast, which would be far from ideal, given the expense of the replacement.
I have suburban 2007 flex with p0171/p0174. It came after p0175 and the injectors changed. The alcohol was 50% and the fuel trim was reset, and it dropped to 3-4% but now it missfire, cant drive, barely idle .Then the other two code came. The new maf, fuel pump, throttle, new ignition cables. Smoke test for leak showed nothing. What can it be?? Evap? Map? Fuel pressure?
There could be a variety of explanations. One common cause is an issue with the feedback sensors on that bank. Another is the presence of an exhaust restriction on one of the banks.
Very informative lecture on fuel trims, i have facing problem in my suzuki Luana asian model it has only map sensor. problem facing is that ltft remains at 10 either the fuel mixture is rich or lean, while stft and total fuel trim responds lean and rich fuel mixture while long term fuel trim remain on 10 , does it proves problem in my ecm ? plz guide !
A LTFT of +10 indicates a correction for slightly lean condition. LTFT is a learned value to accommodate wear and age of the engine and its components. If there are no codes, and the STFT is switching normally across "0", then you don't have a problem. The ECM is happy where it is.
Hello. 2003 Mitsubishi 3.8L V-6, 220,000 trouble free miles. Fuel economy is where it should be. LTFT 1&2 are +12.5% at hot idle. But goes to 0% and stays there when revved to 2,500 rpm. STFT 1&2 are 0% at hot idle. When extra fuel is sprayed on identified leak of intake manifold (leaking o-ring, I used smoke to find) the STFT immediately goes to -6 and then returns when the extra fuel is burned off. Could this intake air leak thats affecting both banks cause the truck to go into a limp mode, giving me these codes? P0335 P2135 P0340 Also, why does LTFT go to 0% when under load? Thanks!
So my 2014 silverado is running -35 on ltft both banks at idle , decreases when rpm increase . That's on a hot engine cold engine running -10 Any idea what may be causing it
Great question! I'm surprised no one has ever asked before. Excerpts from the Bosch Automotive Handbook - The mixture for ideal, theoretically complete combustion requires a mass ratio of 14.7/1. That is, 14.7 pounds of air for every pound of fuel burned. Excess air in the mix is required to ensure there is enough air for complete combustion but there are limits when it comes to burning a mixture that is too "lean". Lambda is a Greek symbol and represents this "excess air" factor. It designates the extent to which the ACTUAL air-fuel. mix differs from the stoichiometric ratio of 14.7/1. It is the ratio of INDUCTED AIR MASS versus AIR MASS REQUIREMENT FOR STOICHIOMETRIC COMBUSTION. A Lambda of 1 indicates that the air mass drawn in by the engine equals the theoretically required air mass. Less than 1 is a deficiency in air mass, or a "rich" mixture and more than 1 is excess air mass or a "lean" mixture.
@@MotorAgeMagazine thank you, that will help me remember what it means better. I was wondering what it meant on my new to me Modis 🤣 I'm really enjoying your shows and learning a lot!
I had a p0171 code set on my 03 , 3.4l Tacoma. When checking fuel trim, The long was showing -18% and short -2.3 to + 1.6 % at idle(680) rpm. I thought a p0171 code would carry a high positive on the long trim? I checked fuel pressure and got 43 psi and it stayed steady when increasing rpm. I have ruled out fuel pump and filter. When raising the rpm from idle to about 2000 rpm, the long will increase to about -3.9 % steady and sometimes go to 0. Would I be correct with these numbers, thinking it's a dirty/clogged fuel injector? The downstream o2 is original with 140k on it. It was carrying .300 range on scanner. Excellent Video Motor Age!
Yes, you're right - I would expect positive trims if a System Lean code was set. And it may be, since this is a V6 correct? There should be trim numbers for both banks. Try this: 1. Check Freeze Frame to learn what the conditions were when the code set (idle, cruise, hot, cold?). 2. Look at trims for both banks and send those over - check at idle and 2000 rpm for now.
Yes, V6. Think I solved the problem. I changed the upstream sensor which is called air/fuel sensor and I replaced the mass air flow sensor. The sensor appeared to be fine but I bought it off Ebay and it was listed as OEM Denso. I noticed the part number was 22204-22010. I got a part number from dealership and there's was, 22204-21010. The one from Ebay was a knock off! I installed the new true OEM mass air flow sensor and BOOM! My fuel trims and read... long, -3.1 at idle and drop to zero at 1,500 rpm and short remained the same. The hesitation when tramping on the throttle is gone. I only have 1 short and 1 long trim reading on my scanner doing live data. I am thinking it's only one fuel rail feeding all 6 cylinders? Thank you for the response! I am learning much from your videos!!
Thanks for the explanation as I am trying to figure out if my car is running properly. The RPM just goes under 700 when idle and sound of the engine of course changes. There is also some fuel smell coming from the tail pipe when doing 10+ min idle. After driving for some time, parking and smelling the exhaust, it doesn't smell at all. I did capture live data(15 min drive) and if I give you the link, will you be able to help and look at that data?
I don't really see anything in the data except some strange readings from the MAF sensor. Cleaning very rarely fixes one that has become contaminated. However, I also see some strange PIDs on the data list you sent. I've never heard of Bank 3 for example. You might want to look at the information with a better quality tool first.
@@MotorAgeMagazine Thank You! I will try another scan tool and/or the app. I don't know if MAF was contaminated or not, but as preventive maintenance I cleaned it to see if it was the reason my vehicle went below 700 at idle(at times). Could you please tell me about strange readings with MAF you saw, so I can troubleshoot and look at my options?
I'm chasing a stubborn P0507 Code on a '05 Grand Prix Series 3- 3800 Non-Supercharged. I also have a LTFT of 25 and a STFT of 16 at idle. Which usually means a vacuum leak... I've smoked the engine... I see no leaks..... I've switch out the TB and the MAF with one known to be good. I've replaced the PCV and it's gaskets. The Intake manifold gaskets have been replaced recently. All the "usual" things regarding this code I have done..... I just can't seem to find the cause............................other ideas, that why I'm watching this EGR video......?? BTW.... the engine seems to run fine... until the CEL comes on and it goes into Limp Home Mode.
A couple of questions - Is this equipped with an IAC or APP? What is the actual throttle position versus desired? Second, what happens to fuel trims if you raise RPM up to 2500 or so? Any other codes?
Man on a 3.8l mustang v6 I have both banks running rich. I've cleaned the maf, checked fuel pressure while the vehicle is running and unplugged the fuel pressure regulator vacuum line. The test said that the FPR was good. Could the maf actually be shot? Any way I can test it?
Typically, one bank will be correcting for a lean condition and the other, a rich condition. Remember, a MAF sensor measures ALL the air going into the engine and doesn't distinguish between banks, or cylinders. Even if one cylinder on one bank has breathing issues, the ACTUAL amount of air on that bank is not the HALF of the total you may expect. Have you tried a Volumetric Efficiency test to see if the engine can breathe properly?
I have both short term bank 1 25.0 Short term bank 2 25.0 then both goes back down to 0.0 when i push the gas then go back up to 25.0 what could this be
The assumption is of course that the New car has a 0 fuel Trim I would like test a brand new car Fuel Trim data, can bet it wont be 0. Also the algorithms programmed into the ECM is based on certain standard data.. air pressure and humidity . If you are in a higher humidity environment like the tropics or sub tropics then the air is going to contain 35% more moisture than say in Seoul Korea. That means less efficient burn, more O2 unburnt = Lean = Positive fuel trim response. e.g. the humidity here the other morning was 80% thats a lot different than would have been programmed into the ECM's algos. I also like to gather 20 minutes live driving data, wich is about 1,100 data points, calculated ave Net fuel trims against each load, then graph that. It gives a totally different picture than just observing live Trims.
STFT is not a static number but 31% certainly seems to be correcting for a lean condition. What is the Long Term Fuel Trim? Look at both at idle and again at 2500 rpm and tell me the numbers.
@@MotorAgeMagazine thanks for the speedy replie appreciate it its in the 1st stages of storm barra but I'll let you know the no,s buddy this was at idle passed emissions just but bought a scan tool and learning about what does what 👍👍
Since the title is fuel trim you should probably start with fuel trim and maybe talk about other things but then you should end it with fuel trim there's a short-term fuel trim and there's a long term fuel trim in the short term more or less effects the long-term in the long term fuel trim should always be really close to zero in the short term or the quick fuel trim is usually going up or down is that indicates if you have a problem or not if it's showing that your fuel trim is high or it's putting in more gas that probably means you have a leak in the intake system somewhere and if your fuel trim is going down to keep it at zero or even zero is even then maybe you're one of one of your fuel trims fuel injectors is stuck open and putting in too much gas so the computer is trying to lower the fuel in the engine.
I have a code on car 017011 on an astra h 2004 the air mass sensor has been replaced could the oxygen sensors need replacing ? Or is it somthing else I have read that the code means fuel trim to lean ?
@@katelanstewart3362 Look at the total fuel trim (STFT + LTFT) at idle and at 2500 rpm. If you see high positive correction at idle but normal at 2500, suspect a vacuum leak. If it's ok at idle but off at 2500, check fuel delivery. If off across the board, check inputs to the ECM
I have an 04 acura tl that doesn't idle as smooth as it should. I used a Bluedriver and found my bank 1 trim is 3% and bank 2 is 9%, could this be why? Could it be air leak or sensor isn't good?
@@MotorAgeMagazine I had a pending misfire code on 2 rear cylinders, and one time I accelerated hard to pass someone and the check engine light flashed
NO BODY can help me. My 2000 Explorer 4.0 106k has all sensors in a normal wave O2 & STFT +- BUT the LTFT is high and will max does not change much at idle or out on the road. There are no vac leaks. Smoke test actually popped the glove used on the intake it's so tight. Fuel psi seems normal at 50 psi no return system.
@@MotorAgeMagazine ST waves -4 to +5 as do the O2's. LT is +15 at idle & max'd +25 at take off from stop. In park, LT will stay about +15 at 2k rpm. No vac leaks...I swear. No zippy power like it used to have. Never ragg'd on being wifes trucky-wucky yanno. How can ST be at -3 (both sides always same same) while LT is at +25 under load on Highway? The LT changes/adjusts almost as quickly as ST. I doosh'd the MAF (CRC MAF doosh) it swings .01 to .03 snap throttle.
@@MotorAgeMagazine Pinched off vac line going to EVAP system. Fuel trims began to improve right away. Will smoke test the EVAP system to find a vac leak I swore wasn't possible.
If you are looking at Short Term Fuel Trim (STFT), it means the ECM is in fuel control and feeding the appropriate gasses to the catalytic converter. If it's the sensor reading itself, I'd need more detailed vehicle info to help.
Thank you for such a quick response! It says "O2B1S1" and the reading was fluctuating around 3.200 area. I didn't think that was possible. It's a 2001 Toyota Tacoma V6 with 160k miles. I'll most likely start by replacing the sensor, but I wondered what direction I should head if that's not it. Thanks again!
@@CAREERMAN70 What you're reading is the voltage of an Air/Fuel Sensor or Wideband O2 Sensor. This is not the same as the older designs and the 3v reading is normal. We actually have a story coming up in our August issue on how these designs work. Look for it online at MotorAge.com!
@@MotorAgeMagazine Oh! Okay. Thank you! I flushed out my mass air flow sensor with electronics cleaner. Hoping that might be it. We'll see, I guess. Thanks again!
I'm having an issue with my old truck such that the system ECU is reading like the engine is running rich and adjusting fuel trims negative (LT Fuel Trim = -22) but then i'm getting power drops and stutters like the engine is running too lean. When i hook up the scan tool the o2sensor is oscillating between aprox 23 and 920mv so not an issue with the o2sensor. Any idea what would cause this issue?
First, graph the fuel trim over a test drive - see what its doing at idle, cruise and WOT, along with the oxygen sensors and other parameters that define what the fuel calculation will be. What type of system are you working on - MAF or speed density? That also makes a difference.
@@MotorAgeMagazine I graphed but don't know how to make anything out of the results. They OBD1 doesn't seem to allow graphing but i have put the data in a sheet and looked at it. but don't know what it is telling me. CSV of the data is here: LT FUEL TRIM ,LT FUEL TRIM Div%,ST FUEL TRIM ,ST FUEL TRIM Div%,THROTTLE(%) ,TPS SENSOR(V) ,VEHSPEED(MPH) ,"MAP(""HG) ",O2S(mV) 124,-4,124,-4,4,0.51,42,10.47,932 105,-23,131,3,34,1.55,44,19.73,133 132,4,121,-7,34,1.55,49,19.51,218 126,-2,121,-7,34,1.55,51,19.4,746 122,-6,120,-8,26,1.25,53,16.9,209 115,-13,124,-4,27,1.35,54,15.92,53 117,-11,131,3,28,1.37,55,17.44,107 119,-9,128,0,25,1.31,57,17.11,861 118,-10,125,-3,20,1.06,57,14.28,901 122,-6,120,-8,20,1.08,58,15.04,440 119,-9,124,-4,17,0.92,58,13.95,155 117,-11,121,-7,4,0.51,58,8.61,932 126,-2,118,-10,4,0.51,51,7.74,946 125,-3,118,-10,3,0.51,34,8.61,919 119,-9,129,1,2,0.51,19,10.58,511 105,-23,127,-1,12,0.8,19,14.72,27 123,-5,134,6,31,1.47,26,20.17,173 118,-10,148,20,57,2.27,34,23.43,67 126,-2,129,1,22,1.16,42,20.27,173 122,-6,130,2,34,1.57,46,24.63,817 131,3,124,-4,24,1.2,49,23.54,857 122,-6,117,-11,12,0.76,51,17.77,200 107,-21,124,-4,10,0.75,51,12.21,213 106,-22,130,2,9,0.71,51,12.1,626 106,-22,131,3,16,0.98,51,16.68,844 121,-7,128,0,4,0.49,51,10.69,910 106,-22,121,-7,3,0.49,41,10.03,852 105,-23,126,-2,2,0.49,25,11.12,870 125,-3,123,-5,1,0.49,9,11.45,884 121,-7,128,0,0,0.49,0,12.32,932 126,-2,126,-2,0,0.47,0,12.32,919 126,-2,125,-3,0,0.49,0,12.32,946 125,-3,127,-1,0,0.49,0,12.1,959 125,-3,124,-4,0,0.49,0,12.1,941 123,-5,122,-6,0,0.49,0,12.76,71 121,-7,120,-8,0,0.49,0,14.17,764
@@OlaGbolahan The oxygen sensors were notorious on those for problems. Try unplugging the upstream sensor and driving the truck. If the problem goes away, replace the sensor.
@@MotorAgeMagazine I have a list of codes I can get with the check engine light but its not helping me now in my situation the car runs perfect when it cold and it will set and idle rev up up and down cold or hot but when it's hot and you're driving it likes the stutter like a bad fuel fuel injector I need to see what's happening when computers doing the work ( I have no codes or check engine light )
Thank You 🙏 Your videos are keeping this “Old Timer” relevant in today’s Automotive world, you have no idea how much this helps me, 45 years of wrenching and I’m learning more now than ever.
Pete, thank you for another excellent video. I agree 100%, fuel trim, or in my neck of the woods "mixture adaptions" are a vital in engine diagnostics. I am looking forward to next month!
I just had those codes show up on my 2002 Toyota. Ran the MAF procedure from their Service Bulletin and saw that it was out of spec. Replaced and fixed. Apparently it was under reporting the air weight.
To me this is kind of the confusing part because what the computer says it's kind of the opposite of what's happening if the computer said it's adding more gas that could mean that you have a air leak on the intake side like then take manifold gasket or you have a hose and one of the vacuum lines or something so it's adding more gas to make up for the air leak on the other hand if you would have a fuel injector that was sticking open and it's leaking fuel then the computer would be reading a lean or more air or more air to kind of compensate
I just fixed my car with a P0171. Did almost every test and came to the conclusion that my fuel filter was the culprit. It can literally be a million different things. Fuel trims are your best friends. Along with 02 data
@@DevonWayne some only have one fuel filter built into the fuel tank/ pump and are only replaced when dropping the fuel tank? I don't like that design yuk
@@robertmedina6875 Robert tengo una ??? Tengo una Pilot 2003 Te hago esta ?? Porque no creo que el Don del vid conteste.. Mi problema es el bank #1 no funciona Mientras el bank #2 si.he cambiado lo que Trabaja en in lado al otro y sigue con lo mismo. Desconecto el bank #2 y tiro a prender y enciende Con el bank #1 conecto el #2 y deja de funcionar. Hoy Hice otra prueba. Desconecté el plug del Injector #1 bank #1 y la unidad falla lo conecto y recupera. Le desconecto la corriente a la bobina y el cylinder se queda igual. Está bien weird esto. El short trim del bank #1 está en -27. algo% Se que lo hace la comp pero de donde viene la señal para ese comportamiento????? Ahh! Y la miras y el motor está como si fuera normal quieto en tres cylindros👣 Tiene nuevo todo lo relacionado con.... 👀👃👀Acepto comentario de cualquiera que interese en ayudarme. Pero que tengan LOGICA please!!!! Thanks👈
I’ve tried everything. New o2 sensors. Smoke test and no vacuum leaks. New injectors, new fuel pump, and still getting the po171 and short term fuel trim at like 30% at idle.
I hope EVs,. with less moving parts don't have to deal with all this silly feedback mess. but we all know how that goes the manufacturers will overcomplicate it somehow.
I'm chasing a stubborn P0507 Code on a '05 Grand Prix Series 3- 3800 Non-Supercharged. I also have a LTFT of 25 and a STFT of 16 at idle. Which usually means a vacuum leak... I've smoked the engine... I see no leaks..... I've switch out the TB and the MAF with one known to be good. I've replaced the PCV and it's gaskets. The Intake manifold gaskets have been replaced recently. All the "usual" things regarding this code I have done..... I just can't seem to find the cause............................other ideas, that why I'm watching this EGR video......?? BTW.... the engine seems to run fine... until the CEL comes on and it goes into Limp Home Mode.
Hey I’m just a parts salesman who uses a scanner daily this video has helped me tremendously understanding dtc’s. In instances were I would’ve sold a spark plug, maf sensor or 02 sensor for a trouble code, now are instances of bad vacuum lines and air leaks that are more apparent seeing and understanding now. Thanks again great video
What I found confusing was the term fuel trim. Note, to trim, means to me to cut back, as in trim the bushes. So I was only thinking in black and white, instead of like adding decorations to the Christmas tree...duh. so why not have the best of both worlds when it comes to fuel trim. Trim up or trim down, whatever the case maybe. Now who's the boss, it's the mechanic calling the shots to make it all work like it should..!
Thanks so much for making this great and awesome video on fuel trims! I love seeing your Christian fish symbol! I really got a laugh from God's message: What part of "Thou Shall Not..." don't you understand! So true! God Bless You! 🙏😀
I just had a flashback to my "salad" days of 1998. Motor age and motor magazine were like gold to me.. Sadly all the knuckle headed so called techs, shop managers, and owners I've been around were damn near illiterate. Frickin morons. "Dude what you need that vantage for", types. Before subscribing to these mags every issue I got my hands on became part of my personal library. Repeatedly read cover to cover. What a journey it has been. You're either eager to learn everything you can about this biz with a smile on your face, or the parts cannon will break your vertebrae in no time and your tech career will become a fantasy.
Solid video. Im getting a pending B2 lean code occasionally but the B2S1 voltage is fine and active. The LTFT is around 11. I doing see any other redflags....... curious what the ECU is seeing/understanding. Thoughts? Thanks!
What causes my LTFT to be at +10.8, I drive for half hour, shut engine off, 30 minutes later I start the engine and the LTFT is now +14.1 and stays there while driving half an hour? STFT varies +/-4%. According to my scan tool, the MAF (4.5 g/s) and O2 sensor appears to be working properly. I haven't been able to find a vacuum leak. Fuel pressure is at 40 PSI. Stock 2002 Mustang GT. Injectors never have been changed. No codes. Car drives fine otherwise. Someone mentioned that it could be intake manifold gaskets.
I will start by saying I do appreciate your videos. they are very insightful. however.. All this stuff is going to be obsolete in about 10 years. all this technology and all these sensors are supposed to make diagnosis simplier. but it's never simple. a code indicating a bad O2 sensor, is never about an O2 sensor you have to always find out what it is. that makes all this technology worthless because it just adds more time to diagnosing issues when it could be designed in to just tell you what the problem is like it should. We would hope that new tech/EVs, with ostensibly fewer moving parts, will make these ridiculous and unreliable things like feedback loops the thing of the past. But we all know better. The manufacturers will overcomplicate this somehow, & right quick for sure
Can a can of fuel injector cleaner (Purple max) in a tank holding just 5 gallons (so very concentrated) contaminate the O² sensors resulting in LTFT of 18%
I think this guy just likes to talk about every little thing I don't know if anybody can follow him but the engine is really critically measuring the fuel rate burn with about five different sensors before and after the engine in the O2 sensors really a heat sensor we say it's oxygen I'm not sure why they say that but it measures the heat because it generates a heat electrical signal if we call that at oxygen sensor or an O2 sensor but it measures the heat like most sensors except for a vacuum sensor
Please tell me how to what to do about code p06de AES techs don't know how to check and clear this code techs turned off engine light but it came back on.
What the hell is talking about turn the volume down and watch his hands his hands one hand dances up and down and the left hand dances up and down and then you got both hands dancing up and down and then he's sticking his fingers on his ears his hands and tell you the story He's got the dancing hands
The mass air flow sensor measures the temperature of the air and the temperature of the air means are certain volume of air that's going into the engine it's the temperature measure
Hello, I have a 2000 camry 2.2l with high postive long term fuel trim at 20% at idle, but at higher rpm it drops to 5%, but I cannot find a leak, would a exhaust manifold or intake manifold leak would cuase this? I also have do NOT have check engine light on.
I'm Considering replacing my O2 sensors for wide ban sensors in my 007 Lexus IS350 with 170,500 miles. Last year I replaced my air intake tube with a RR-RACING carbon fiber tube and a K&N proformance air filter and breathable crank case filter. I've just recently started getting P0174 & P0171 codes. I'm using a Cheap "Blue Driver" scanner, but it offers the codes I need. I just cleaned my MAF sensor thismorning and pkan on clearing the codes and see if they come back. My question is would the ECM adjust and react differently or more accurately with the wide ban sensors installed? And... Would it be worth the investment to change the injectors? Thanks in advance Jeff Grant Mooresville NC USA
Short answer - your front sensors are likely already wideband sensors. Sorry to say that you’d be surprised at how many times I’ve traced a fuel trim issue to aftermarket cold air intakes. The turbulence created in them can cause the MAF sensor readings to bounce all over the place. Hope this helps
This has just made it easier for me to explain fuel trim to a customer. Got a Holden Commodore that’s it stft bouncing between 30% and 130%. O2 sensors are shagged! Not codes either.
![Short Term and Long Term Fuel Trims Explained [Easily]](http://i.ytimg.com/vi/IuM53mlOgHs/mqdefault.jpg)
Look old man, I’ve been a senior master ASE tech/mechanic for over 25 years, after listening to you going on and on about your diagnostic theory I feel the need to say…… thanks. I’m still learning. Just subscribed and I’ll be going through all your previous videos and checking in for new ones as well.
Give me a carb any day and get rid of O2 sensors map sensors maf sensors. All to confusing for me.
Great explanation. Best 20 mins I’ve spent on UA-cam in my life.
That was one of the most useful 20 minutes of my life! Amazing presentation both in terms of content and delivery style. You have a new subscriber.... (with a new Creader VIII diagnostic tool).... Thank you :-)
I have tried numerous times to explain this to rookies. I must say that I would not make a very good teacher. That is why I refer them all to either watch your videos or find out more info on their own. Believe me also that you can also teach an old dog new tricks. Thanks again, this is a great video. Keep them coming.
Thanks for the kind words! I'll do my best!
Great video. I learned it slightly different but, basically the same in that the computers response could be compared to an old style tv. The short term is like a fine tuning and the long term is like changing the channel when the fine tuning reaches its limit.
Very nice presentation from the ground up- helps so much in understanding how it all fits together!
You run into people that are true Teachers/Trainers in life, AND you Sir are one of them. Thank You
Thank you for those kind words - I'm glad you find the content helpful.
11:30
Thanks for this excellent video. I need some of your expert guidance. 2011 Hyundai Sante Fe engine failure126,000 connecting Rod bearing failed. Warranty engine installed by Hyundai. 6000 miles later engine lacks power. Finally I get a check engine code PO106 defective map sensor. Replace it with a OEM Hyundai map sensor . Check engine light goes off.No
change in running condition . Vehicle is towed to the dealer Dealer. Dealer diagnosis, 2 defective CATS melted and coming apart inside. I claim the ECU was not communicating with new engine or updated when it was installed. We were probably driving vehicle for many miles with a faulty map sensor( making the engine run lean or rich) but the check engine light never came on and when it finally did it was to late the cats were compromised. My other reason the CATS failed is when the original engine blew up it sent engine parts ( rod bearing, connecting rod , piston and engine block)coolant, oil and fuel right into the CATS compromising them. It’s now a battle with the dealership trying to get them to replace the CATS under the engine warranty. Dealer checked the ecu with a basic scan And says its working. No check engine light currently on and no codes For catalytic converters . The dealer also ran a compression test 140,160,160,160. Not sure if this imbalance would affect the AFR in each cylinder? Any advice Appreciated
Thank You
Yes Sir, Indeed !!!
One of the best field trip backsplashes I listen to ready for the next class thank you
Great explanation of fuel trims using hand gestures. I now have a better understanding
Best video on UA-cam period. Thank you Sir!
Thank you!
Wonderful instruction. Thank you for sharing you time and knowledge.
You just explained ,very simply and articaly what I have tryed to explain to young people I have worked with.
Most of them and customers when you mention 02 sensor they think that it can't be causing there problems .Not to mention like you said you can go from a bad 02sensor or bad coil and end up with a destroyed catalytic converter all because of a simple problem and then the crying begins and how stupid what ever car company who built the car is .A car being worked on right now 2005 Mazda tribute .
With 3 kats ,it started with a misfire to bad coils ,was driven quite awhile like that .Needless to say ran scan .short term and long term fuel trim1 all at 0 .and a open loop fault
With all upstream 02 sensors.
And a whole lot more .just by looking at every thing on the scan tool kats are blocked EGR tube and EGR blocked
Great tutorial thank you 👍
Good Afternoon Pete Meier motor age Take care and have a great day 👍
From Nick Ayivor from London England UK 🇬🇧
There's only one feedback sensor and that's the old two sensor which really is amazing because it's measuring the oxygen or the heat coming out of the engine the heat is indication of the oxygen if that makes sense that's how they get a sense of reading is by the heat
Basically the whole sensors react to temperatures they just measured in a different way the old two sensor the oxygen sensor creates a voltage between .1 and .9 and this gets the computer the signal of the heat in the exhaust and we call it an oxygen sensor.
The fuel trim is showing you what the computer is doing to keep the engine running at efficiency if the computer is saying that you have more gas going in then that can mean you have a air leak in your intake system it's trying to balance it out so what's more critical is if the long-term fuel trim is not at 0 or neutral then you really have a big problem the short-term fuel trim should be going up or down a little bit to control the burn of the fuel which is pretty much measured by the heat of the O2 sensor and the heat of the O2 sensor which we call the oxygen in other words if you have a high signal you're not getting enough gas if you're getting a low signal you getting too much gas and you can imagine the O2 sensor only puts out a 0.9 volt to a 0.1 volt so you can imagine how close it monitors the heat of the exhaust gas coming out of the engine I would think you need an O2 sensor for each cylinder but it's happening so quick that you only need one per six or four cylinders or eight cylinders it depends on the manifold if you have 202 sensors they just last longer because you have two manifolds exhaust manifolds
Excellent job, thank you sir
Always learning something . good info
Hey. Superb video. I have strange problem with short fuel trims. My engine is BMW M54B30. On bank 1 i got +25-28%, but on bank 2 it is ok 0 to 5%. I know that my oxygen sensor after cat on bank1 is dead. Is this can affect on fuel trims?
MAF is working, I checked rubber hoses and there is no cracks.
Help please. Thanks.
Short answer - yes, the rear sensor can impact fuel trims. Replace the sensor and recheck.
Thanks so much Pete
If your not sure how rich (or lean) the ratio is, would unplugging the MAF sensor be a way to reduce harm to the cat? Would it bring it back to default mix?
I've just had a new cat fitted today, yet now see a prior 'too rich' code and a Maf voltage too low code. So am now concerned that the new cat will burn out fast, which would be far from ideal, given the expense of the replacement.
Wish he would tune my truck , he’s smart very smart
Every code is a top-10 DTC
You Sir, are a wonderful mechanic!
I have suburban 2007 flex with p0171/p0174. It came after p0175 and the injectors changed. The alcohol was 50% and the fuel trim was reset, and it dropped to 3-4% but now it missfire, cant drive, barely idle .Then the other two code came. The new maf, fuel pump, throttle, new ignition cables. Smoke test for leak showed nothing. What can it be?? Evap? Map? Fuel pressure?
Did the lean codes occur AFTER the alcohol reset? Did you verify that the alcohol content of the fuel?
Hello what about if my long and short term stay at 0%
Could you explain why bank1 and bank2 performance (staff t and ltft) can be so different in a 2005 Tacoma prerunner with over 151k
Thanks
There could be a variety of explanations. One common cause is an issue with the feedback sensors on that bank. Another is the presence of an exhaust restriction on one of the banks.
This is great content thank you
Very informative lecture on fuel trims,
i have facing problem in my suzuki Luana asian model it has only map sensor. problem facing is that ltft remains at 10 either the fuel mixture is rich or lean, while stft and total fuel trim responds lean and rich fuel mixture while long term fuel trim remain on 10 , does it proves problem in my ecm ?
plz guide !
A LTFT of +10 indicates a correction for slightly lean condition. LTFT is a learned value to accommodate wear and age of the engine and its components. If there are no codes, and the STFT is switching normally across "0", then you don't have a problem. The ECM is happy where it is.
EXCELLENT THANKS
Closed loop is the same as make ready?
Hello. 2003 Mitsubishi 3.8L V-6, 220,000 trouble free miles. Fuel economy is where it should be.
LTFT 1&2 are +12.5% at hot idle. But goes to 0% and stays there when revved to 2,500 rpm.
STFT 1&2 are 0% at hot idle. When extra fuel is sprayed on identified leak of intake manifold (leaking o-ring, I used smoke to find) the STFT immediately goes to -6 and then returns when the extra fuel is burned off.
Could this intake air leak thats affecting both banks cause the truck to go into a limp mode, giving me these codes?
P0335
P2135
P0340
Also, why does LTFT go to 0% when under load? Thanks!
So my 2014 silverado is running -35 on ltft both banks at idle , decreases when rpm increase . That's on a hot engine cold engine running -10
Any idea what may be causing it
A few questions. Does this use a MAF sensor (I think it does)? What are the STFT numbers under the same conditions? Are there any related codes set?
Great Job !!
Great job
Damn dude awesome video...
What does the word "LAMBDA" actually mean? 🤔
Thanks for the great series.
Great question! I'm surprised no one has ever asked before. Excerpts from the Bosch Automotive Handbook - The mixture for ideal, theoretically complete combustion requires a mass ratio of 14.7/1. That is, 14.7 pounds of air for every pound of fuel burned. Excess air in the mix is required to ensure there is enough air for complete combustion but there are limits when it comes to burning a mixture that is too "lean". Lambda is a Greek symbol and represents this "excess air" factor. It designates the extent to which the ACTUAL air-fuel. mix differs from the stoichiometric ratio of 14.7/1. It is the ratio of INDUCTED AIR MASS versus AIR MASS REQUIREMENT FOR STOICHIOMETRIC COMBUSTION. A Lambda of 1 indicates that the air mass drawn in by the engine equals the theoretically required air mass. Less than 1 is a deficiency in air mass, or a "rich" mixture and more than 1 is excess air mass or a "lean" mixture.
@@MotorAgeMagazine thank you, that will help me remember what it means better. I was wondering what it meant on my new to me Modis 🤣 I'm really enjoying your shows and learning a lot!
I had a p0171 code set on my 03 , 3.4l Tacoma. When checking fuel trim, The long was showing -18% and short -2.3 to + 1.6 % at idle(680) rpm. I thought a p0171 code would carry a high positive on the long trim? I checked fuel pressure and got 43 psi and it stayed steady when increasing rpm. I have ruled out fuel pump and filter. When raising the rpm from idle to about 2000 rpm, the long will increase to about -3.9 % steady and sometimes go to 0. Would I be correct with these numbers, thinking it's a dirty/clogged fuel injector? The downstream o2 is original with 140k on it. It was carrying .300 range on scanner. Excellent Video Motor Age!
Yes, you're right - I would expect positive trims if a System Lean code was set. And it may be, since this is a V6 correct? There should be trim numbers for both banks. Try this: 1. Check Freeze Frame to learn what the conditions were when the code set (idle, cruise, hot, cold?). 2. Look at trims for both banks and send those over - check at idle and 2000 rpm for now.
Yes, V6. Think I solved the problem. I changed the upstream sensor which is called air/fuel sensor and I replaced the mass air flow sensor. The sensor appeared to be fine but I bought it off Ebay and it was listed as OEM Denso. I noticed the part number was 22204-22010. I got a part number from dealership and there's was, 22204-21010. The one from Ebay was a knock off! I installed the new true OEM mass air flow sensor and BOOM! My fuel trims and read... long, -3.1 at idle and drop to zero at 1,500 rpm and short remained the same. The hesitation when tramping on the throttle is gone. I only have 1 short and 1 long trim reading on my scanner doing live data. I am thinking it's only one fuel rail feeding all 6 cylinders? Thank you for the response! I am learning much from your videos!!
dave jones Glad you found the problem !
Thanks for the explanation as I am trying to figure out if my car is running properly. The RPM just goes under 700 when idle and sound of the engine of course changes. There is also some fuel smell coming from the tail pipe when doing 10+ min idle. After driving for some time, parking and smelling the exhaust, it doesn't smell at all. I did capture live data(15 min drive) and if I give you the link, will you be able to help and look at that data?
I can try...be sure to inclde make, model, year and mileage.
@@MotorAgeMagazine Thanks! Just sent you 2 links with car info to Facebook link you had in the description.
I don't really see anything in the data except some strange readings from the MAF sensor. Cleaning very rarely fixes one that has become contaminated. However, I also see some strange PIDs on the data list you sent. I've never heard of Bank 3 for example. You might want to look at the information with a better quality tool first.
@@MotorAgeMagazine Thank You! I will try another scan tool and/or the app. I don't know if MAF was contaminated or not, but as preventive maintenance I cleaned it to see if it was the reason my vehicle went below 700 at idle(at times). Could you please tell me about strange readings with MAF you saw, so I can troubleshoot and look at my options?
I'm chasing a stubborn P0507 Code on a '05 Grand Prix Series 3- 3800
Non-Supercharged. I also have a LTFT of 25 and a STFT of 16 at idle.
Which usually means a vacuum leak... I've smoked the engine... I see no
leaks..... I've switch out the TB and the MAF with one known to be good.
I've replaced the PCV and it's gaskets. The Intake manifold gaskets
have been replaced recently. All the "usual" things regarding this code
I have done..... I just can't seem to find the
cause............................other ideas, that why I'm watching this
EGR video......?? BTW.... the engine seems to run fine... until the
CEL comes on and it goes into Limp Home Mode.
A couple of questions - Is this equipped with an IAC or APP? What is the actual throttle position versus desired? Second, what happens to fuel trims if you raise RPM up to 2500 or so? Any other codes?
I found the problem ...it was a bad brake booster....
Man on a 3.8l mustang v6 I have both banks running rich. I've cleaned the maf, checked fuel pressure while the vehicle is running and unplugged the fuel pressure regulator vacuum line. The test said that the FPR was good. Could the maf actually be shot? Any way I can test it?
What are your fuel trim numbers at idle - at 2500? That's one place to start...OR you can join me tonight! ua-cam.com/video/Gc-41R9Gp8s/v-deo.html
My gpm is gone down so bad and I was hoping obd2 will show me the sign of what is the cause of that
are you asking about gallons per mile or miles per gallon?
What to look for in case of exhaust restriction. Both banks sensors fluctuating about .7 v
Thanks
Typically, one bank will be correcting for a lean condition and the other, a rich condition. Remember, a MAF sensor measures ALL the air going into the engine and doesn't distinguish between banks, or cylinders. Even if one cylinder on one bank has breathing issues, the ACTUAL amount of air on that bank is not the HALF of the total you may expect. Have you tried a Volumetric Efficiency test to see if the engine can breathe properly?
I have both short term bank 1 25.0 Short term bank 2 25.0 then both goes back down to 0.0 when i push the gas then go back up to 25.0 what could this be
I'm betting your engine uses a MAF sensor. If that's the case, my initial suspicion would be a vacuum leak.
The assumption is of course that the New car has a 0 fuel Trim I would like test a brand new car Fuel Trim data, can bet it wont be 0. Also the algorithms programmed into the ECM is based on certain standard data.. air pressure and humidity . If you are in a higher humidity environment like the tropics or sub tropics then the air is going to contain 35% more moisture than say in Seoul Korea. That means less efficient burn, more O2 unburnt = Lean = Positive fuel trim response. e.g. the humidity here the other morning was 80% thats a lot different than would have been programmed into the ECM's algos. I also like to gather 20 minutes live driving data, wich is about 1,100 data points, calculated ave Net fuel trims against each load, then graph that. It gives a totally different picture than just observing live Trims.
Am in UK and stft is 31% is this my 02 or possible o2 failure this is what my scan tool says I have a vauxhall omega 2.2 👍
STFT is not a static number but 31% certainly seems to be correcting for a lean condition. What is the Long Term Fuel Trim? Look at both at idle and again at 2500 rpm and tell me the numbers.
@@MotorAgeMagazine thanks for the speedy replie appreciate it its in the 1st stages of storm barra but I'll let you know the no,s buddy this was at idle passed emissions just but bought a scan tool and learning about what does what 👍👍
@@stevebarker1974 I'll be looking for the info. Let me know if any codes are set - or pending.
@@MotorAgeMagazine just one code mil p0650 also 02 is reading 744.50mv that's bank 1 but I'll gather all necessary info many thanks
Since the title is fuel trim you should probably start with fuel trim and maybe talk about other things but then you should end it with fuel trim there's a short-term fuel trim and there's a long term fuel trim in the short term more or less effects the long-term in the long term fuel trim should always be really close to zero in the short term or the quick fuel trim is usually going up or down is that indicates if you have a problem or not if it's showing that your fuel trim is high or it's putting in more gas that probably means you have a leak in the intake system somewhere and if your fuel trim is going down to keep it at zero or even zero is even then maybe you're one of one of your fuel trims fuel injectors is stuck open and putting in too much gas so the computer is trying to lower the fuel in the engine.
I once had a converter overheat on a 1986 Chevy Caprice . It was a bad alternator putting out low amps causing the rpm not to reach proper speed.
Makes no sense to me, Kevin.
I have a p0171 code on my 99 Toyota Camry with a cylinder misfire
I have a code on car 017011 on an astra h 2004 the air mass sensor has been replaced could the oxygen sensors need replacing ? Or is it somthing else I have read that the code means fuel trim to lean ?
Did you lost that code correctly?
@@MotorAgeMagazine I read the code correctly it had other codes to do with the air mass so changed it just got that code now from the pedal test
@@katelanstewart3362 Can you send info on the code definition? Not familiar with it.
Just read the code means the fuel trim is running to lean ?
@@katelanstewart3362 Look at the total fuel trim (STFT + LTFT) at idle and at 2500 rpm. If you see high positive correction at idle but normal at 2500, suspect a vacuum leak. If it's ok at idle but off at 2500, check fuel delivery. If off across the board, check inputs to the ECM
I have an 04 acura tl that doesn't idle as smooth as it should. I used a Bluedriver and found my bank 1 trim is 3% and bank 2 is 9%, could this be why? Could it be air leak or sensor isn't good?
Any codes?
@@MotorAgeMagazine I had a pending misfire code on 2 rear cylinders, and one time I accelerated hard to pass someone and the check engine light flashed
@@KenyonPayne The flashing MIL indicates a severe misfire. Fix that first...
@@MotorAgeMagazine it's only done that once a month ago, it must have only done it very briefly as I didnt even hear of feel a misfire
@@KenyonPayne Most likely your rough idle is related. I suspect something mechanical...possibly head gasket leak. Do you have to add coolant?
NO BODY can help me. My 2000 Explorer 4.0 106k has all sensors in a normal wave O2 & STFT +- BUT the LTFT is high and will max does not change much at idle or out on the road. There are no vac leaks. Smoke test actually popped the glove used on the intake it's so tight. Fuel psi seems normal at 50 psi no return system.
Let's start at the beginning. What are the STFT and LTFT at hot idle? What are they at 2500 rpm? Are the STFTs switching either side of zero?
@@MotorAgeMagazine ST waves -4 to +5 as do the O2's. LT is +15 at idle & max'd +25 at take off from stop. In park, LT will stay about +15 at 2k rpm. No vac leaks...I swear. No zippy power like it used to have. Never ragg'd on being wifes trucky-wucky yanno. How can ST be at -3 (both sides always same same) while LT is at +25 under load on Highway? The LT changes/adjusts almost as quickly as ST. I doosh'd the MAF (CRC MAF doosh) it swings .01 to .03 snap throttle.
@@MotorAgeMagazine Pinched off vac line going to EVAP system. Fuel trims began to improve right away. Will smoke test the EVAP system to find a vac leak I swore wasn't possible.
I have a reading of 3.93+/- on my bank 1 O2 sensor. What does that mean?
If you are looking at Short Term Fuel Trim (STFT), it means the ECM is in fuel control and feeding the appropriate gasses to the catalytic converter. If it's the sensor reading itself, I'd need more detailed vehicle info to help.
Thank you for such a quick response! It says "O2B1S1" and the reading was fluctuating around 3.200 area. I didn't think that was possible. It's a 2001 Toyota Tacoma V6 with 160k miles.
I'll most likely start by replacing the sensor, but I wondered what direction I should head if that's not it. Thanks again!
@@CAREERMAN70 What you're reading is the voltage of an Air/Fuel Sensor or Wideband O2 Sensor. This is not the same as the older designs and the 3v reading is normal. We actually have a story coming up in our August issue on how these designs work. Look for it online at MotorAge.com!
@@MotorAgeMagazine Oh! Okay. Thank you! I flushed out my mass air flow sensor with electronics cleaner. Hoping that might be it. We'll see, I guess. Thanks again!
I'm having an issue with my old truck such that the system ECU is reading like the engine is running rich and adjusting fuel trims negative (LT Fuel Trim = -22) but then i'm getting power drops and stutters like the engine is running too lean. When i hook up the scan tool the o2sensor is oscillating between aprox 23 and 920mv so not an issue with the o2sensor. Any idea what would cause this issue?
First, graph the fuel trim over a test drive - see what its doing at idle, cruise and WOT, along with the oxygen sensors and other parameters that define what the fuel calculation will be. What type of system are you working on - MAF or speed density? That also makes a difference.
@@MotorAgeMagazine I graphed but don't know how to make anything out of the results. They OBD1 doesn't seem to allow graphing but i have put the data in a sheet and looked at it. but don't know what it is telling me. CSV of the data is here:
LT FUEL TRIM ,LT FUEL TRIM Div%,ST FUEL TRIM ,ST FUEL TRIM Div%,THROTTLE(%) ,TPS SENSOR(V) ,VEHSPEED(MPH) ,"MAP(""HG) ",O2S(mV)
124,-4,124,-4,4,0.51,42,10.47,932
105,-23,131,3,34,1.55,44,19.73,133
132,4,121,-7,34,1.55,49,19.51,218
126,-2,121,-7,34,1.55,51,19.4,746
122,-6,120,-8,26,1.25,53,16.9,209
115,-13,124,-4,27,1.35,54,15.92,53
117,-11,131,3,28,1.37,55,17.44,107
119,-9,128,0,25,1.31,57,17.11,861
118,-10,125,-3,20,1.06,57,14.28,901
122,-6,120,-8,20,1.08,58,15.04,440
119,-9,124,-4,17,0.92,58,13.95,155
117,-11,121,-7,4,0.51,58,8.61,932
126,-2,118,-10,4,0.51,51,7.74,946
125,-3,118,-10,3,0.51,34,8.61,919
119,-9,129,1,2,0.51,19,10.58,511
105,-23,127,-1,12,0.8,19,14.72,27
123,-5,134,6,31,1.47,26,20.17,173
118,-10,148,20,57,2.27,34,23.43,67
126,-2,129,1,22,1.16,42,20.27,173
122,-6,130,2,34,1.57,46,24.63,817
131,3,124,-4,24,1.2,49,23.54,857
122,-6,117,-11,12,0.76,51,17.77,200
107,-21,124,-4,10,0.75,51,12.21,213
106,-22,130,2,9,0.71,51,12.1,626
106,-22,131,3,16,0.98,51,16.68,844
121,-7,128,0,4,0.49,51,10.69,910
106,-22,121,-7,3,0.49,41,10.03,852
105,-23,126,-2,2,0.49,25,11.12,870
125,-3,123,-5,1,0.49,9,11.45,884
121,-7,128,0,0,0.49,0,12.32,932
126,-2,126,-2,0,0.47,0,12.32,919
126,-2,125,-3,0,0.49,0,12.32,946
125,-3,127,-1,0,0.49,0,12.1,959
125,-3,124,-4,0,0.49,0,12.1,941
123,-5,122,-6,0,0.49,0,12.76,71
121,-7,120,-8,0,0.49,0,14.17,764
@@OlaGbolahan What is the year/make/model of your truck? I didn't realize it was OBD I - that changes things a bit!
@@MotorAgeMagazine it is a 93 Chevy K1500 5.7 Ltr v8 40L60E
@@OlaGbolahan The oxygen sensors were notorious on those for problems. Try unplugging the upstream sensor and driving the truck. If the problem goes away, replace the sensor.
Wide band vs linear type 😉
my cars are a 1992 and a 1994 jeep xj no code here
Your vehicles are OBD I. Back in those days, each manufacturer had their own codes and code definitions. But it still had the same job - emissions.
@@MotorAgeMagazine I have a list of codes I can get with the check engine light but its not helping me now in my situation the car runs perfect when it cold and it will set and idle rev up up and down cold or hot but when it's hot and you're driving it likes the stutter like a bad fuel fuel injector I need to see what's happening when computers doing the work ( I have no codes or check engine light )
White Scott Martin Dorothy Moore Laura
why is there only 311 comments ? this channel is LEGENDARY, or is it above the heads of most 'TECHY'S ' ?? keep up the great work, BLESS 👍😍
Thank You 🙏 Your videos are keeping this “Old Timer” relevant in today’s Automotive world, you have no idea how much this helps me, 45 years of wrenching and I’m learning more now than ever.
Absolutely Outstanding videos You are an amazing instructor! Thank You Thank You Thank You !!!
Just bought a blue driver scan tool and wanted to learn. then i found you! Awesome channel ! I'm a new sub. Thanks for the wisdom !
Pete, thank you for another excellent video. I agree 100%, fuel trim, or in my neck of the woods "mixture adaptions" are a vital in engine diagnostics. I am looking forward to next month!
Well said Sam R. M.
Always the very best love you videos all of them period.
I just had those codes show up on my 2002 Toyota. Ran the MAF procedure from their Service Bulletin and saw that it was out of spec. Replaced and fixed. Apparently it was under reporting the air weight.
Nice ! Awesome explanation of fuel trims Pete !
Thanks Billy, and thanks for taking the time to comment.
Looking forward to the next one. And many thanks for tackling my fuel pump waveform question a few months back.
Thanks you for this video, you explain things very well!
Very informative. Explains everything very thoroughly. Excellent tutorial!
To me this is kind of the confusing part because what the computer says it's kind of the opposite of what's happening if the computer said it's adding more gas that could mean that you have a air leak on the intake side like then take manifold gasket or you have a hose and one of the vacuum lines or something so it's adding more gas to make up for the air leak on the other hand if you would have a fuel injector that was sticking open and it's leaking fuel then the computer would be reading a lean or more air or more air to kind of compensate
I just fixed my car with a P0171. Did almost every test and came to the conclusion that my fuel filter was the culprit. It can literally be a million different things. Fuel trims are your best friends. Along with 02 data
I've been assuming that's it for me also. However, fuel filters dont exist for me SUV. Wtf!? No auto parts store or even online. Super weird
@@DevonWayne some only have one fuel filter built into the fuel tank/ pump and are only replaced when dropping the fuel tank? I don't like that design yuk
@@robertmedina6875 Robert tengo una ???
Tengo una Pilot 2003 Te hago esta ??
Porque no creo que el
Don del vid conteste..
Mi problema es el bank #1 no funciona
Mientras el bank #2 si.he cambiado lo que
Trabaja en in lado al otro y sigue con lo mismo.
Desconecto el bank #2 y tiro a prender y enciende
Con el bank #1 conecto el #2 y deja de funcionar.
Hoy Hice otra prueba. Desconecté el plug del
Injector #1 bank #1 y la unidad falla lo conecto y recupera.
Le desconecto la corriente a la bobina y el cylinder se queda igual.
Está bien weird esto.
El short trim del bank #1 está en -27. algo%
Se que lo hace la comp pero de donde viene la señal para ese comportamiento?????
Ahh! Y la miras y el motor está como si fuera normal quieto en tres cylindros👣
Tiene nuevo todo lo relacionado con....
👀👃👀Acepto comentario de cualquiera que interese en ayudarme.
Pero que tengan LOGICA please!!!!
Thanks👈
I’ve tried everything. New o2 sensors. Smoke test and no vacuum leaks. New injectors, new fuel pump, and still getting the po171 and short term fuel trim at like 30% at idle.
I hope EVs,. with less moving parts don't have to deal with all this silly feedback mess.
but we all know how that goes the manufacturers will overcomplicate it somehow.
I'm chasing a stubborn P0507 Code on a '05 Grand Prix Series 3- 3800
Non-Supercharged. I also have a LTFT of 25 and a STFT of 16 at idle.
Which usually means a vacuum leak... I've smoked the engine... I see no
leaks..... I've switch out the TB and the MAF with one known to be good.
I've replaced the PCV and it's gaskets. The Intake manifold gaskets
have been replaced recently. All the "usual" things regarding this code
I have done..... I just can't seem to find the
cause............................other ideas, that why I'm watching this
EGR video......?? BTW.... the engine seems to run fine... until the
CEL comes on and it goes into Limp Home Mode.
many thanks, a good explanation and a good heart
This is a very comprehensive explination of fuel trims and how short term and long term fuel trims relate.
Hey I’m just a parts salesman who uses a scanner daily this video has helped me tremendously understanding dtc’s. In instances were I would’ve sold a spark plug, maf sensor or 02 sensor for a trouble code, now are instances of bad vacuum lines and air leaks that are more apparent seeing and understanding now. Thanks again great video
Thank you for taking the time to educate yourself and not just blindly sell parts
good point. Too many salesmen just want to sell without fully understanding the purpose of the part.
New sub explained in an incredible easy to comprehend explanation, Thank you. At 70 I can still find well explained info.
Great vid.👍👍👍👍
What I found confusing was the term fuel trim. Note, to trim, means to me to cut back, as in trim the bushes. So I was only thinking in black and white, instead of like adding decorations to the Christmas tree...duh. so why not have the best of both worlds when it comes to fuel trim. Trim up or trim down, whatever the case maybe.
Now who's the boss, it's the mechanic calling the shots to make it all work like it should..!
No. Trim means to 'Shape ' in this case. Not reduce.
Thanks so much for making this great and awesome video on fuel trims! I love seeing your Christian fish symbol! I really got a laugh from God's message: What part of "Thou Shall Not..." don't you understand! So true! God Bless You! 🙏😀
I just had a flashback to my "salad" days of 1998. Motor age and motor magazine were like gold to me.. Sadly all the knuckle headed so called techs, shop managers, and owners I've been around were damn near illiterate. Frickin morons. "Dude what you need that vantage for", types. Before subscribing to these mags every issue I got my hands on became part of my personal library. Repeatedly read cover to cover. What a journey it has been. You're either eager to learn everything you can about this biz with a smile on your face, or the parts cannon will break your vertebrae in no time and your tech career will become a fantasy.
It would be good to show some examples.
Great and very helpful lessons. Well elaborate. Thanks
Solid video. Im getting a pending B2 lean code occasionally but the B2S1 voltage is fine and active. The LTFT is around 11. I doing see any other redflags....... curious what the ECU is seeing/understanding. Thoughts? Thanks!
Fantastic Video! I subscribed to your channel. Thank you for making these highly educational videos.
Been studying your videos past few days thank you for your wisdom and knowledge I appreciate it
What causes my LTFT to be at +10.8, I drive for half hour, shut engine off, 30 minutes later I start the engine and the LTFT is now +14.1 and stays there while driving half an hour? STFT varies +/-4%. According to my scan tool, the MAF (4.5 g/s) and O2 sensor appears to be working properly. I haven't been able to find a vacuum leak. Fuel pressure is at 40 PSI. Stock 2002 Mustang GT. Injectors never have been changed. No codes. Car drives fine otherwise. Someone mentioned that it could be intake manifold gaskets.
I will start by saying I do appreciate your videos. they are very insightful. however..
All this stuff is going to be obsolete in about 10 years.
all this technology and all these sensors are supposed to make diagnosis simplier. but it's never simple. a code indicating a bad O2 sensor, is never about an O2 sensor you have to always find out what it is. that makes all this technology worthless because it just adds more time to diagnosing issues when it could be designed in to just tell you what the problem is like it should.
We would hope that new tech/EVs, with ostensibly fewer moving parts, will make these ridiculous and unreliable things like feedback loops the thing of the past.
But we all know better. The manufacturers will overcomplicate this somehow, & right quick for sure
This was great at helping me understand and diagnose issues with my fuel trim.
Can a can of fuel injector cleaner (Purple max) in a tank holding just 5 gallons (so very concentrated) contaminate the O² sensors resulting in LTFT of 18%
2011 Buick LaCrosse 2.4 ecotec.... My short term fuel trim #2 (O2 Sensor band 1 sensor 2) is always 92% no matter what.
Awesome explanation, thank you!
My long term fuel trim is at 0.00 no movement .
My maf sensors is .001-.002
What could be the issue here ?
I think this guy just likes to talk about every little thing I don't know if anybody can follow him but the engine is really critically measuring the fuel rate burn with about five different sensors before and after the engine in the O2 sensors really a heat sensor we say it's oxygen I'm not sure why they say that but it measures the heat because it generates a heat electrical signal if we call that at oxygen sensor or an O2 sensor but it measures the heat like most sensors except for a vacuum sensor
Please tell me how to what to do about code p06de AES techs don't know how to check and clear this code techs turned off engine light but it came back on.
What the hell is talking about turn the volume down and watch his hands his hands one hand dances up and down and the left hand dances up and down and then you got both hands dancing up and down and then he's sticking his fingers on his ears his hands and tell you the story He's got the dancing hands
I know Sir that you could clear up this problem why is it these AES techs don't know about this code help.
The mass air flow sensor measures the temperature of the air and the temperature of the air means are certain volume of air that's going into the engine it's the temperature measure
Hello, I have a 2000 camry 2.2l with high postive long term fuel trim at 20% at idle, but at higher rpm it drops to 5%, but I cannot find a leak, would a exhaust manifold or intake manifold leak would cuase this? I also have do NOT have check engine light on.
A "leak" is any source of unmetered air entering the engine (that is, after the MAF sensor). Intake manifold leaks are common.
FLAT RATE TEST DRIVE - an excellent idea!
I'm Considering replacing my O2 sensors for wide ban sensors in my 007 Lexus IS350 with 170,500 miles. Last year I replaced my air intake tube with a RR-RACING carbon fiber tube and a K&N proformance air filter and breathable crank case filter. I've just recently started getting P0174 & P0171 codes. I'm using a Cheap "Blue Driver" scanner, but it offers the codes I need. I just cleaned my MAF sensor thismorning and pkan on clearing the codes and see if they come back. My question is would the ECM adjust and react differently or more accurately with the wide ban sensors installed? And... Would it be worth the investment to change the injectors? Thanks in advance Jeff Grant Mooresville NC USA
Short answer - your front sensors are likely already wideband sensors. Sorry to say that you’d be surprised at how many times I’ve traced a fuel trim issue to aftermarket cold air intakes. The turbulence created in them can cause the MAF sensor readings to bounce all over the place. Hope this helps
@@MotorAgeMagazine Thank you for your response! I may consider going back to the OEM parts. Thanks for your advice!!
This has just made it easier for me to explain fuel trim to a customer. Got a Holden Commodore that’s it stft bouncing between 30% and 130%. O2 sensors are shagged! Not codes either.