E46 Negative Fuel Trims Case Study

This 1999 328i would not set it's catalytic converter engine monitor for over a year. There were no DTC codes thrown. This was my process in diagnosing and repairing this problem.
This video is for entertainment purposes only. 50sKid assumes no liability for any repairs or modifications performed by the viewer as a result of the information contained in this video.

[@LSmiata]

Hello 50sKid, Very nice and detailed video. You are very detailed in your approach to diagnosis and I learn much about the BMW engines. As for fuel pressure issue, and checking against five regulators, I would suspect the gauge. To often people believe a poorly calibrated gauge as accurate and it will severally bias actual world conditions of measurement......Yes I am also a QA guy and experience this situation too many times (trusting a bad/out-of-spec) gauge. Thanks again for your videos, P

[@ianmatterson5632]

distracted or not, what a great tutorial you have uploaded fella, jam packed with knowledge, thank you so so much..

[@Dicer328]

Great video. I really appreciate the thought process explanations.

[@aviking1947]

Straight to the point! Thank you not too much talking like other channels. Great explanation

[@12vgs8606]

Great video; really fantastic diagnostic skills displayed here.

[@scobra6674]

Love your videos and love how you don't chop out the misleaders. I like that you follow every step and show us what your doing in detail. Its great to be able to compare your findings with my own. Thanks 50's kid!

[@ericmatheri9394]

When i add fuel, the fuel gauge needle does not move up immediately, just slow as i drive. What could be the issue?

[@evaldassmilgis]

Thanks 50's your video save my money time and from useles jobs, after engine swap we connect wrong lamdas 😀💪👍

[@dexietyy7922]

Mine is difficult to start it takes about 5 seconds of cranking and it stinks like unburnt fuel I’ve got 0 codes but my fuel trims are off and I simply just can’t get to the bottom of it very frustrating

[@stylo8133]

I want to understand one thing. So if you drive long time with a broken o2 sensor the engine wil adapt and make new settings. I have a bad o2 sensor after cat. Engine runs rich. I have cold start problems because long term fuel is -100% . And both short term are -60 while idle. When throttle they went up to -90. So the bad starting cold is due bad o2 sensor?

[@ColeTanner88]

Come on man....with any issue with fuel trims, first step should ALWAYS be to monitor what o2s are doing and simulate a rich/lean condition to see if o2s respond properly. Wasted so much time by pulling injectors and swapping not just one fpr, but 5. I recommend subscribing to scannerdanner premium and buying his engine performance book.

[@jeffreynobles948]

Exactly!!!! Monitor LTFTs, STFTs, as well as HO2 upstream sensor(s). Actually, they are "reactors" more than they are sensors.

[@komentatorius69]

how do you do that? to get rich you turn the MAF of? and to get lean, you take of the ccv hose that goes to the valve cover?

[@pospc2]

@@komentatorius69 i have used a unlit propane torch with a hose on the nozzle to a vaccum nipple to simulate a rich condition. To try and simulate a lean condition i have pulled the brake booster hose off the intake manifold to allow un metered air into the engine. Not sure if these are the correct ways. Try at your own risk. I'm not responsible if you mess up your car or injure yourself or others in any way.

[@zoommair]

Hey 50sKid, love your channel! Question: what's the likely scenario when the long term fuel trims are at negative 8 percent, but short term fuel trim is near 0? That's the situation I have and I'll double-check I have a Siemens Mafs, but curious if the Mafs would cause it for the long-term fuel trims. Thanks for any help!

[@50sKid]

MAF is a possibility. Also bad 02 sensors. Bad fuel pressure regulator (check if fuel pressure is higher than 50). Do the fuel trims get more positive when the RPM is at 3000?

[@zoommair]

I'll have to run the live data on my scanner next time I get a chance, unfortunately I'm still new to looking at live data. It's also been a long time since I did the fuel pressure test, so I might have to do that again to know, because I don't remember if it was higher than 50 or not. O2 sensors are fairly new, so I think you can rule them out. However, when I was looking at the freeze frame data, both long term and short term fuel trims were in the negative, around negative 8-10. So the car is running rich and the ecu is compensating right?

[@garymiller2056]

Fuel trims look good, ZoommaiR. Normal

[@garymiller2056]

You are slightly rich. Short term should move toward positive on the long term (less negative ) if ECU is compensating. After about 30 seconds to a minute.

[@HappyPlaceAquatics]

Good evening I have a 05 E46 that I get a p1500 code that sets. I have replaced the idle speed control valve, the ccv system and intake boots due to being torn. But I can not figure this code out. All my fuel trims are negative in the freeze frame data any help would be greatly appreciated thank you

[@edvinasa9365]

Hello bro, I have problem.. black spark plugs, high fuel consumption, my long term fuel trim is negative -18%, I cant found problem, injectors new, I I tried another maf, o2 sensors. My car is bmw f10 2011m 535i witht n55 engine. Maybe you will face such trouble? No errors.. smoke test done, I checked and cleaned vanos solenoids, install new oem spark plugs etc. Thanks for your advice bro:)

[@JoseFernandez-zt5xs]

Can you tell me what software are you using?

[@kennyspringer7668]

Please help can't figure this one out I have code saying running rich Bank 1 and 2 however Downstream I'm getting an absolute no reading on the fuel trim and negative fuel trim Upstream

[@h1av]

My car reads in INPA, lambdaintegrator 1 -25%, and lambdaintegrator 2 +26%. Do you have a clue? Thank you Sr.

[@UncleLexx]

Thank you, very useful, I have something similar, have clues what to check

[@ILoveCycNails]

hello. SHRTFT1(%) = +6.3 and LONGFT1(%) = -7.0 , is good or bad? Another question: SHRTFTB1S1(%) = 2.3 and SHRTFTB1S2(%) = -100.0, is good or bad? what does "G"?

[@mygoalcrash8077]

Hi this soft sanmastrer is free? Full version?

[@KashifJavedForex]

I have civic 2005 1.5L. It does not have O2 sensor. On OBD2 it does not support STFT/LTFT. How this works in my car?

[@mirajan2486]

zdravim mam oblem z 530 d e39 toči jen 2900 otaček vic ne kde mam hledat problem

[@MobilemechanicPhiladelphia]

No engine light 03 sonato Live read negative fuel trim. -2.3. Long term short term 0 at idle Engine shakey some time like it want to turn off

[@jussimat7223]

Hi, can you tell me where i can order pressure gauge, what does fit in m54 fuel line Schrader valve

[@marcopolo-e7h]

6:35 I didn't see no fuel pressure being lower!!! 😬

[@DillonTurner395]

Awesome video love the detail

[@tmanda323]

Hi Nice vid... What scan tool do you use?

[@thromboid]

Ha - I was thinking all through the diagnosis how working on a two-bank system would make it easier to look for discrepancies...but only a two-bank system could have the swapped leads problem!

[@50sKid]

Definitely helps to have an extra sensor to swap over. Or fuel injectors to swap from bank to bank

[@samvjr07]

good morning 50 skit Klim thank you again for helping us and explaining well how to deal with our cars you mentioned on this video that you have to replace oxygen sensors in pair since my X5 2008 3.0 has 4 oxygen sensor do I need to replace Bank 1 and bank 2 Upstream in pair or do I have to replace one oxygen sensor from bank one and then one oxygen sensor from bang 2 I'm a bit confuse and thanks again.

[@50sKid]

I mean bank 1 and bank 2, either front sensors or back sensors.

[@samvjr07]

50sKid thanks so much..

[@fernandobanda8287]

hey quick question... 02 325i do u think my car would run rough if I remove the stock air box and install a aftermarket cold air intake ? thanks for answering my questions..

[@50sKid]

usually that isn't a problem, unless it's an exceptionally bad aftermarket product and the engine can't breath as well as before.

[@fernandobanda8287]

+50sKid ok thank you very much for replying.

[@borisidijana]

Hey i love your videos and your work, keep it up. I live in the UK and i got an e46 2003 325ci msport auto. Now im getting fuel trim bank 1 and bank 2 permissible range exceeded and fuel trim bank 1 and 2 control limit. I have no vacuum leak, i replaced the top 2 o2 sensors for bosh ones, i replaced the maf sensor for non oem ( völt) brand. The car would have rough idle when the codes do show up, sometimes it would even cut out when approaching a junction or teaffic lights, and when i go from neutral to drive or reverse the revs would go bellow 500rpm for a second and go back up to where it should be. Any thoughts?

[@mikeymagic117]

I'm sure you have now figured it out. This is a classic symptom of a failing camshaft sensor.

[@besofacacia6103]

you never answer but i think wtf ? what you have done is bacicly fixed the ritch condition problem by changing regulator witch showed the same number. maby you did something more and dont remember ? is it possible that after maf replacement ecu corrected trims later then then it should ? i noticed bmw ecu,s are very slow in that term

[@starships7510]

i thought the post cat 02 sensors plug in underneath the car? and pre cat plug in under the hood, its like that on e36

[@50sKid]

yep that's correct, did I misspeak in this video? I don't remember it in detail

[@achristian7015]

I take it you are talking about the Readiness Check.

[@sirsweetness8332]

02 Sienna, 420 code. Does 99.2% B1S2 indicate a bad after cat O2 sensor?

[@50sKid]

You're probably looking at the wrong PID code. Some of them report as 99% which doesn't really mean anything--make sure you're looking at the right thing. Btw a P0420 code almost always means you're gonna be replacing your cat.

[@sammycrack0dirt]

50skid is this different on our m54? When I search for it I get a pipe bomb looking thing with filter built in. Is that correct?

[@50sKid]

Yeah this car was an M52TU--the M54 has the integrated fuel filter/pressure regulator

[@sammycrack0dirt]

50sKid ok that's what I thought. Do you a video on our pump? I couldn't find it. If you don't could you make one?!

[@zekprieinechenanzamqn3219]

Hi there, first thanks for your videos! I have quick question: My 320ci 2000year shoes on board 18L/100 and sometimes goes to 20L/100.. and when i went to scan tool its shoes something like this "Oxygen sensor heater after cat bank 1"

[@zekprieinechenanzamqn3219]

I`ve tested the engine with smoke machine and found sucking jet pump ont the break hose leaking smoke and the distribution piece (equalizer) was broken one of the pins so i fixed it. Went to a guys they deleteed some errors history (not just the codes, because i have scanmaster) so the normalized. But now the oil yellow lamp poped up when i turned the car off so i check the level and it was on the minimum i poured a liter and today i started the car and pulled up the dipstick to chek the level and some WIERD sound was there like bubbling or something like this....?! Gosh im so tired fo this ...do u have any suggestion?

[@zekprieinechenanzamqn3219]

Thanks for the fast answer. I`ve changed the ccv before 6 months. I am so scared :D so I read everthing on the internet and i found some guy saing this "The PCV system will try to suck outside air down the dipstick tube when the stick is removed - because it's continually trying to suck the crankcase out. Disconnect the PCV line and see if the sucking noise goes away. If so, you're just hearing the PCV system working as designed." So make sens, but dont know is this true?

[@davidsavic3090]

The e46 G.O.A.T.

[@rowen898]

Moral of the story - don’t let an idiot work on your car.

[@duanedonaldson2262]

While I am watching. On a straight 6 BMW engine, which cylinders are bank 1, and which cylinders are bank 2 pls. You mentioned it later in the video, thanks. You pulled a vacuum hose from the fuel pressure regulator without testing for a vacuum leak, low vacuum means greater pressure. You then put in a used part, you then changed the part again without getting that repair on camera and not showing the good fuel pressure, and editing the first used part out of the video OMG. No shop rags under the injectors to catch a drip, drip hell, it's a flood, OMG. No worries about the mistake, we all make them hehe. You had the injectors out, I will assume you didn't put a cleaner through them, and you didn't flow rate them or inspect them for a good spray pattern after doing all that work to pull them out, OMG. Nice diagnosis to swap O2 sensors but to get a better reading on your graph, only graph the 2 sensors and not all the other stuff, the more stuff you monitor, the slower and worse your graph on the items that you really need to trace. On a test drive, you should also monitor your throttle so you remember for sure when you accel and when you cruise and when you decel and stop to idle. No need to erase adaptations when you don't have any long term fuel trims, even if you did, they will clear up on a good test drive. Do you trust your fuel pressure gauge that much, where did you get it tested and certified? With other guys saying 54 on their cars, it's good to go. Thanks a lot for the Case Study.

[@fritzz2]

you should have reseted the lambda adaptation when you have changed the o2 sensors

[@mikealkaddumi]

can you do a front seal video? great job man btw👌👌👌

[@lutherkling79]

03 BMW codes are p0171 and p0175....bank one is lean and bank two is Rich....do you have a idea... I'm asking you cause you seem to know a lot about BMWs

[@BimmerDope]

hi 50skid.i am getting STFT1 as -100.8!!!! all the time..stft2 is -1.6 varies closely..LTFT1 and LTFT2 are positive 7 and 7.8.bmw e46 m54.thanx alot for ur precious time to make these videos.what could it be?..and what is normal..i dont think stft1 is normal

[@BimmerDope]

i used elm327 with torque

[@50sKid]

Could be a bad oxygen sensor, bad wiring, or a bad engine computer.

[@gregorytolson4621]

Maybe your pressure gauge is out of calibration

[@icysteve46]

I wish my problem was that easy.

[@scottykilmer1094]

Those Bosch oxygen sensors ar very very bad ! they die quick or they give false readings! If you buying a new sensor always buy Denso !

[@ainsipour2003]

good

[@petroflorence7962]

Cnek for exhaust leak near sensor at back of car little leak send sensor crazy

[@mattlane2282]

Lets explain this a little better... READINESS MONITORS are just monitors that state if a test cycle was completed or not, if you reset the computer, the computer needs time to determine if everything is working correctly, that is what that READINESS monitors state... Also that fuel pressure did not change AT ALL if anything it was HIGHER with the new regulator...

[@stewartfamily3981]

Mines is -19

[@robertrukidding3055]

Your videos are usually quite good and the video quality on this one is stellar......however. Who the hell looks at fuel trims on a 200% scale?? After the O2 fix you had them at 100 and 200%. Completely meaningless as far as gleaning anything from this. Also you sure wasted a lot of time in diagnostic time not looking for O2 response, worrying about a 5psi pressure difference etc.. Just some tough love, but keep up the good work.

[@mridware9694]

Hahhahahahaha if fuel injector will leak then car will not start easily

[@jbaroli]

Very good video. As a suggestion, I think it is a good idea to reset adaptation every time you modify something, for example the O2 sensors or a change in fuel pressure due to a FPR. You save time in that adaptation. I´m working on a 99 328i E46 with negative fuel trims as well.

[@juancarlosm5746]

Thanks for posting the missed diagnosis as well... A real professor!

[@aor3200]

That was one great success. In my opinion, not so easy to resolve. I have to try this scanmaster for livedata. Keep up good work and keep E46 on the road, those are great cars.

[@jb6574]

You do realize you couldve just pulled the vacuum line on the regulator and observerd fuel pressure gauge for changes

[@nepovemvam5731]

These engines work on constant fuel pressure. It's not a vacuum line but a vent line so in case of diaphragm failure the leaking fuel would have somewhere to go. If he pulled that line nothing would have changed.

[@jso726]

Great video, very organized and to the point, I'm subscribed, keep it up man!

[@Kunta1926]

It’s the opposite actually. If it’s a bad maf your fuel trim will continue to go down while engine rpm increase.

[@akanecortich8197]

Bad MAF at normal speed will under estimate the air entering, as expected by the TPS and ECU. Thus mixture will turn out to be lean because of more actual air, causing an increase in fuel input. However I guess the MAP would then record a higher air pressure than assumed by they same TPS and also make additional adjustment via ECU. I always wonder if the Fuel Trim reading is the Sum of all the adjustments made in the ECU (MAP MAF 02), or just the O2 sensor result. I would think the Fuel Trim figure would have to be the Net result of all the ECU adjustments from input from the MAF MAP and 02, since it is meant to be indicating the net fuel increase/decrease over the mean.

[@imdfonz]

This is an awesome diagnosis step ny step why negative fuel trims. What would you do differently to get hete earlier? GREAT VIDEO. DONT COMMENT MUCH BUT GREAT WORK!!@@@

[@adolfosalazar7889]

Bro on part 3:20 of this video could that just affect 1 bank if it's a v6 engine like could an aftermarket MAF sensor cause -50 short term fuel trims on Bank1 and on Bank2 at (0)

[@JS-ri2rx]

Great video. I have a 1.8 Vauxhall.never thought of changing o2 sensors in pairs. But food for thought. The scan data graph being on a pc was alot larger and clearer and great I could the difference in bank 2. Well done and thanks

[@1jeffr]

You would think BMW would make the wiring to each sensor different lengths so that the sensors couldn't be inadvertently switched.

[@Rebak714]

Hey 50skid what about when all STFT AND LTFT are all negative what does that mean?

[@nadeem5476]

ONE THING that is bothering in mind that when the Long term fuel trim is already coming in NEGATIVE it means the ECM is cutting the Fuel that much percent , OK understood but when the FUEL is cut already that much percent WHY still it is showing in negative ? it should be to ZERO around bcz the excess fuel is already CUT . why it is always showing negative ? no sense i think . what you say . ?

[@JMUDoc]

Negative trims means 1. over-fuelling - fuel pressure too high, leaky injector/s, 2. under-burning - weak coil/s, fouled or faulty plug/s, or 3. air intake blockage (not likely)

[@carloscortez3836]

Hey man can you help me? I had a cold intake down to the bottom and it was raining for a day here in California, no longer have the weather guard by the tire. Well, the filter got wet and as i was driving home from work the car kept losing power and wanting to die out, the car died but started back up and i proceed to go slowly home. i made it home and let it sat for a day and convert back to a short ram intake. But now it car feels sluggish and once i get to 5k rpm the power cuts out. I plug in my scanner to check short fuel trims. once I get to 5k the power cuts out. It shows -17 Short term. So, what that means is its running rich and is taking too much fuel out right since its 17- and that's when I lose power. I did have a check engine light for a EVAP Canister Purge Control Valve leak before, but it was fine

[@nadeem5476]

hi my car Reports negative ten long term fuel trim ONLY AT IDLE as I push gas pedal little bit like 1200 rpm or 1500 rpm the long term fuel trim comes to negative 3 or less immediately ! any one can tell me why it shows negative ten at idle only?

[@WV591]

my sentra 2005 has made me pull what's left of my hair the past 4 months. all started with simple P0171.nothing has worked including smoke leak tests and MAF sensors ans WB O2 sensors and other junk.

[@bandan4392]

Why were you unplugging and switching O2 sensors for the front sensors but you were talking about the rear sensor?

[@vasilbachev6592]

Fuel pressure I the same 54psi before and 54psi after!?!?

[@adolfosalazar7889]

And can a bad fuel pressure regulator only affect one bank thnks in advance

[@porcha42a]

I had a similar problem. I replaced the pre and after cat sensor, fixed everything.

[@JJ-sv1ov]

Could have done the fuel pressure leak down test with injectors in place or am I missing something?

[@del9936]

How does the scan master talk to the car ,do you get a blue tooth dongle or something?

[@isrealperez9069]

I have to watch the video the second time and I'm still having the same kind of problem

[@5riverz365]

Ur absolutely right at 3:20. Cant put cheap aftermarket stuff on bmws. When i bought my car it had some cheap aip electronics maf on it and i spent 6-7 months off n on trying to figure out the fuel trims being maxed at like -25%. One day i just happened to be checking the intake tubing and i saw the lil ghetto resister in the maf in place of the element. Switched it out and issue was actually positive trims

[@50sKid]

Yep! Very common, you just gotta be careful about what cheap parts you use.

[@lx4118]

I have -10 for my fuel trims at 2000 rpm and 0 at idling, what can it be ?

[@MarkSmith-js2pu]

Why wouldn’t you care about LT trims after all those rides?

[@jb5222]

Thanks for this buddy still very useful video

[@markpoposki]

Hello sir, love your videos and have been a sub since day 1. Had a question for you. I have a bmw z3 with lean codes. Car has extensive service history. Had it for 12 years. To diagnose the problem i smoked it, no leaks. I watched your video on fuel trims and my situation is very odd. Trouble codes are p071 p074-lean bank 1 and 2. Short term FT are -6/-7 for bank 1 and 2 Long term fuel trims are 11.7 for both banks. And they stay 11.7 with rpm at 2.5k. Interesting thing is short term fuel trims go up to + 7 with rpms going up to 2.5k O2 sensors. I’m getting normal reading for both bank 1 pre and post cat sensors. Bank 2 o2 sensors stay at .8 value. I’m really confused. I did order maf cleaner and fuel pressure tester. What should I check next. What do you think is the culprit here? Thank you!

[@hiromiya3365]

What does Alldata tell you about fuel pressure.

[@aor3200]

Great success!

[@damaestro5667]

What were the symptoms ?

[@fernandobanda8287]

what did u use to do the live scan ? I belive u used a laptop, is that something anyone can get or is it only license mechanics that can get it? Your videos are very helpful. thanks ....

[@50sKid]

The hardware is ELM327 cable from eBay (it's a buggy knockoff that drives me crazy because it doesn't always work). The software is Scanmaster ELM.

[@Eddythe_Eagle]

I have a Autel MD802 Scanner that suppose to transfer data to a lap top! I have not tried it yet to see haoe well it works. If you purchase this model it will do live data. I paid about $260.00 Cdn at Amazon Canada. i did a lot of research. If you want this type of function. You will need to pay more. By the way Banda this scanner will also diagnose tranmissions. The more you pay the more it does. This is a technician grade intrument. You will need to spend a lot of hours learning how to use it. So far I like what I see. Sofware is live time and is free. It covers many Asian, Eropean, domestic cars. I hope this helps you!

[@tjaymoor6789]

what software are you using??

[@danielandujar5479]

Hi I have a Q! Honda pilot 2003 3.5 Negative fuel trim issue. I have only 2 sensors for both banks. My problem is on bank #1 pcm shutt down this bank completely Both sensors are reporting Short term -27.3% S1. Fluctuations 0.940V. 0.630V. I think is rich. S2. 0.035V. 0.140V mostly stayed 0.035V I think is lean. But bank 2 is working normally can't tell the reading my scanner Don't shows. But the evidence on spark plugs are visible. And on bank #2 you disconnect each wires from coils and they miss. On bank #1 don't. But if I disconnect bank #2 completely. Then pcm put #1 bank to work... This is weird!!!! Can you help me on this please?? Any Advice??? Take your time but please answer !!! Thank's

[@joeespisito9200]

Another regulator in the tank

[@jolgiiis]

Hey, I have recently bought a 316i e46 (N42B18 engine) and I've got some problems with the oxygen sensors... Currently the oxygen sensors are swapped (according to realoem) but if you swap them to their correct positions I end up with a fault code saying they are swapped. Disconnecting the bank 2 cable gives a fault code saying that the bank 2 sensor is disconnected. Any help would be greatly appreciated! Ps. I've learned a tonne from your videos and I watch them like a teenage girl watches Netflix.

[@yep3729]

I hate stupid mechanics!

[@mvilla4614]

Hello 50'sKid...I have three codes right now which are Po17,Po172 & P0041. After watching this video, my question is could that be my problem??? I just had those same two O2 sensers replaced a few weeks ago. I drove to cycle the code out, and it cleared. I then replaced the OE lower and upper intake boots, and the MAF(aftermarket). All codes cleared, drive seems back to normal, then all of a sudden I get the three codes. P0172,P0175, & P0041....NEED HELP ASAP TO TRY AND FIX THIS PROBLEM. Do you think the O2's were maby plugged in wrong?HELPHELPPLEASE THANKS

[@ninofajardo1288]

I do have a long term fuel trim of -7% on e46 m3. When i rev it up to 2000rpms steady. my short term back goes to -22% and my car starts stuttering. This is not evident when im driving underload or WOT. Short term bank stays between - +5% on idle and while driving. Only under steady rpm with car not moving it jumps -22% and stutters. Any idea what this could be? I have been trying to figure this out for awhile now.

[@robeaton2191]

HI 50s kid great video, what would be the likely cause of very high lean condition (25 for both banks short term from cold) and after 20 mins of driving the bank 1 drops to normal levels whereas the bank 2 remains at 25, should i be looking at 02 sensor voltage output? Thanks

[@matbes30]

Hello, I'm having a weird issue, my bank 1 short term is between -100% and -90% at idle, when going 5k rpm it drops to -50%. Only on bank 1. Long terms are both on -6.3%. When opening the oil cap, short bank 2 goes up while the bank 1 doesn't move. Does anyone have an idea? Thanks !

[@navinkaria4338]

Hi 50s kid , really good videos i tried to find out a fix for my car BMW 3 series but cant find any issue , please sir if you could advise me . I had an OBD trouble code which is ( P1168 Post Catalyst Fuel Trim System Correction Value above Threshold (Bank 1) . Best regards

[@sasacvetkovic127]

It is strange that long term fuel trim is 0, at the start of the video. That can indicate that you have a problem with fuel sistem. And when you switch places on rear bank O2 sensor it starts to work as it should, and they corrected long term fuel trim to -3. I also have LTFT fixed zero, and trying to find the solution. Unfortunately i have one pre cat and one after cat O2 sensor, and they are connected as they should. My car has 0 for LTFT, and i am searching for the solution. Ana idea where to start?

[@segbachan5123]

I got a Buick enclave and I have negative 100 on bank 2 for both short term and long term trim. O2 sensors and fuel pressure is good. I also have no codes and bank 1 tests very good..any thoughts , cheers

[@zilanabid5931]

I got a 98 528i and I was working on the fuel filter and somehow I broke a plastic pc of the pressure regulator valve and it’s kinda too expensive to buy a whole new one is there any other solution for itt like if the spectre ones I can work with?

[@xawierymorgan4611]

i have negativ trims at idle (-3,5%) and positiv while driving +4,5% . WTF ?

[@ukaszteter6283]

Have you repaired the car?

[@marukthomasian6309]

does replacing the battery reset the Cat Monitor fuel trims are sightlynegative .1-.2 % and the MAF reads 4.7 g/s and car runs fine will the cat mpnitor go off after a long drive? Thanks I love your videos.