I had to diagnose a stalling problem on a 95 Stratus 3.5. Long story short fuel trim max high bank 1 and then max lean on bank 2. When reset it would run for a few minutes until the trims would do it again but sometimes swap sides. Long story short the engine had been swapped with 1 year newer and bank 1 & 2 were reversed in the harness on that year model. Computer would see bank 1 go lean and enrich bank 2, bank 2 seen rich and lean bank 1 some more. That was a fun one.
Hey Dan I know this video is a couple of years old but it just saved me over $2000 dollars. 2006 Acura TL 216,000 miles P0420 catalyst below threshold bank 1. But short term and long term fuel trimmed maxed out. Downstream sensors were reading lean condition.Sprayed carb cleaner to verify downstream o2 sensors were working. They were. Long story short coolant temp sensor was +40° off. Making the ECU think the car was hotter than it was and giving less fuel. Which the o2 sensors were reading and ecu trying to compensate with fuel trim. No 02 sensor replacement ($200 × 4) no catalytic converter replacement ($600 ×2). I do my own work (free). $30 coolant temp sensor fixed everything. Cant thank you enough. If you're ever in NYC I owe you a ton of beers.
I am watching this video over and over again. Amazingly that other shop replaced a common part that would affect both banks (the MAF sensor) when the vehicle only had an issue with bank 1. Too many parts replacers out there in the industry without "diagnostic" skills. I see it as "keep on throwing parts at the vehicle till the problem goes away"...sorry, but not on my wallet. I love these videos!
You have been my great teacher,since i started following u up i have improved i lot in my career as auto electricians. I want to say a big thanks to u.
Thanks to your videos I learned to look at my data and it helped me to diagnose an 05 Infiniti with a long crank time and lean readings on both o2 sensors. No lean codes were stored and car ran perfect when it started.
Just discovered your awesome channel. I guess the answer to your question is the fact that there is no throttle valve on this particular model. That role is taken by the Valvetronic system.
Not to mention the safety risk and health effects. My shop refused to provide us with safety glasses, mask, ear plugs or knee pads. They provide a cheap safety shoe once a year so if you worn it out, they wont replace it for you. The gloves they gave are cheap cloth ones, not oil resistant nitrile. Used engine oil causes cancer
Poor pay? My tuner charger me 1100 for 4 hours of dyno tuning. Y'all charge 80 to 120 per hour for labor. How's that poor pay? I was a mechanic for the army for 14 years. It's not hard labor. And tuning requires knowledge. But that's it.
This is a very good video presented in a methodical manner. To answer your final question about why that engine had pressure in the manifold it is a valvetronic engine. As a former BMW trained technician the initial give away is the bulge in the valve cover. Not sure if you have done a video on that system as this is the first off you videos I have seen Regards Ian
Watch your videos a lot. You are the best! As a long time shop owner I often use your instruction to help my techs to never forget the basics! Your breakdowns are awesome! Thanks for all you do for our industry!!!
Very informative... After replacing my injectors, I started noticing backfiring.. I never thought a lean condition could cause that.... Your video has inspired me to send the injectors off to be tested and after I replace them, I'll check my O2 sensors. Thank you
@@Diagnosedan Great thanks to your wife, otherwise we never know if you would try to prove yourself opposite by explaining us thinks in such an excellent way. So, when she says so, let's think this is the way how she develops your talent.
@@Diagnosedan all wifes are the same. Women, they hate each other, and they're partners/husbands (after a while..) because we share and admit the clever among us, while them/they're, nothing like that.. brotherhood of man. And I swear I am not misogin..
I have been driving myself insane troubleshooting a failed smog on my 98 boxster. Fuel trim negative, indicating rich. But downstream shows 0.1 or 0.05, lean. This video explained clearly that it's likely an upstream. Untill now I have been watching voltage instead. Thanks for the help.
Great video, Dan. I'm a long-time self-taught garage mechanic working mostly on German cars, especially on BMW's. And I'm also learning even more by just watching this video. To answer your bonus question, I think there is still a slight vacuum after you remove the MAP sensor, or else, this Naturally Aspired combustion simply won't work. And the reason that even when you articulate an artificial leak in the intake manifold and still maintained a stoich condition is because of BMW's VALVETRONIC system in place. Under the VALVETRONIC system, the throttle body no longer plays a key role in intake air control. In fact, you can have the throttle body fully open the whole time and it won't make a difference as long as the O2 sensors are properly working and nothing being wrong with the fuel supply. Actual fine control of the air is done by the intake cams which is fully modulated by the VALVETRONIC system.
Awesome video thank you Dan the man . System bmw came out with I believe it’s called vanos which requires no throttle plate so that engine rpm is changed through variable valve lift
Now in my sixties and having left the auto technician career behind (25 years ago) for tool and die, I'm thinking of a return. Of course it'll be my own shop. Who would hire an old guy? With your ability to explain various systems you've brought back my mojo. I totally understand you. Thank you for these videos. You are an inspiration.
Hi Dan, great videos. My car has a sudden 20% increase in fuel consumption, but no other noticeable changes or codes. This is more noticeable when the engine is cold, but still higher than normal at operating temp. My long term fuel trim stays between 5.5 and 10.9 (normally the low is 8%, it only takes very short dips to 5.5), and short term stays between -2.5 and 1.5. I think I have a lazy o2 sensor - the manual recommended it to be changed 20,000 km ago. Upstream is wideband, LAMBDA normally stays at 1 while cruising, but sometimes bounces between .9 and 1.1. It will spike to 2 when throttle goes from high to close. mA normally is around 0.7, but will spike to 3.2 when throttle goes from high to close just like LAMBA. Downstream is regular o2, when car is warming up it stays low around .005. It climbs as engine is warming and then stays around 0.7 while idle and bounces between .1 and .9 while driving. I have no signs of a bad catalytic converter, so should I just replace both sensors?
Well I'm not a fan of just replacing parts. The numbers your giving me ain't great but not to bad either. See if the fuel trims improve with higher Rpm's. Also check your temperature sensors!
@@Diagnosedan Hey, I forgot to come back to tell you! I started monitoring my coolant temp and noticed it always stayed between 170-185 when warm without any symptoms of an open thermostat. I pulled the temp sensor and it was covered in a film. Changed it out for $5 and my car is running great again! You da man Dan!
A another easy to understand lesson. Thank you for all your sacrifices you made in order to offer these videos to us! I Can't stop watching your videos, they're so contagious! :-)
Awesome video, So many great uses for brake cleaner lol... another way to verify O2 and A/F ratio sensor operation from the driver seat (on vehicles with vacum power brakes) is to pump the brake pedal rapidly for a few seconds, this will force the system lean and when you stop pumping the brake pedal the system will go rich for a little bit. All you have to do is monitor the sensors and see which one is not responding 😊
That BMW uses a Valvtronic system. Basically it can control valve lift electronically which pretty much eliminates the need for a throttle plate and this is the reason there is no vacuum at the manifold because air flow is controlled by controlling valve lift instead of a throttle plate. This system is very similar to what Nissan Calls VVEL (vairable Valve Electronic Lift). It's pretty slick.
A quick question Dan, can you tell a narrow band from a wide band just by looking at them. Just watched this video of yours for the 4th time. Brilliantly explained. I’ve even shared it with my work colleagues. You’ve even started a catch phrase in my garage. When I fix something I turn to the other guys and say “ diagnose Paul fixed it again”🤣
Ha ha thats awsome! Narrowband sensors usually have 4 wires and wideband sensors usually have more. If you follow this rule your right 95% of the time😉 Thanks for the comment DiagnosePaul💪
thank you for the video I've had a hard time finding good explanations of wideband, narrowband, and the relation between the two with new systems that use both oxygen sensors for fuel trims. Next is Biased Voltage sensors.
Great content in this video! I am surprised that BMW does not have a back up fuel strategy for circumstances like this, a lot of the Asian vehicles use downstream fuel trims when they have a upstream wideband
This reminds me of the time I had to diagnose a 1990 Dodge pickup with V8 and automatic. When cold and warming up, ran great. Once it reached operating temperature, it would chuff and chug and misbehave. The single O2 sensor was heated, and internally it bled 12V to the sensor wire forcing it to go rich. New O2 sensor fixed it!
Diagnose Dan, you are the MAN!!! I ran across one of your videos the other day and I am such a fan now. You are exactly what the new generation needs as a common sense back to basics teacher. You are mandatory must watch for my younger crew. Keep doing what you do and we will keep subscribing, watching and spreading the word!!!
It's interesting... Always new guys need learn old knowledge. I have tried to figure out how this works for a couple of weeks, and even though I have looked at this video sometimes, I have forgot it and the video. But now I have to copy the whiteboard information into my notebook! 😁 Maybe I then can get more information from the data shown in certain apps, otherwise we have to improve the apps. How difficult can that be? Dan, you are an angel, or you was also five years ago. One difference, you looked somewhat younger five years ago... 🥺
Excellent explanation ,I now understand how it works. Is there a quick and easy way to identify which type of sensor we are testing? I assume that a wide band sensor has more wires than a narrow band sensor but is there anything else to look out for identification? Just found one of your previous answers to the same question, should have read further. Thanks for a brilliant video.
Awesome and very clear explanation! It was like I was in school! Subscribed! Also I was wondering who has answers on that last one, why the non-turbocharged BMW has positive air pressure on idle and not vacuum?
Excellent!! But in your drawing u have the Lambda line vertical. I’m not understanding that. It seems it should b horizontal at approx 500 millivolts on the narrow band. Like as if it was graphed on a scope. That was the only thing that confused me. I really like that Lambda on the wide band. I’ve said this before. A great teacher is able to make a complicated subject seem simple!!
Hi Dan what a great lesson I like the way you explain every detail. I have a question about narrowband 0² Sensor. In this video the bank 2 downstream 0² sensor is reading .7 volts. Does the reading is normal or it is a little bit rich? Cause it is close to 1v. Thank you and God Bless.
A quick question Dan, can you tell a narrow band from a wide band just by looking at them. Just watched this video of yours for the 4th time. Brilliantly explained. I’ve even shared it with my work colleagues. You’ve even started a catch phrase in my garage. When I fix something I turn to the other guys and say “ diagnose Paul fixed it again”🤣 12 DiagnoseDan
You see i am not having any such problem on my car, i am not even a mechanic, however i really enjoy your shows. They are informative and nicely presented. You are way better than lots of teachers and some tv shows.
I guess it's an engine with BMW's Valvetronic system which regulates the amount of air the engine takes so no throttle valve (actually there is but for emergency situations only) on it. Intake valves act as throttle valve(s). So quasi atmospheric pressure can be measured inside the intake plenum.
Well I didn't know what Valvetronic is since I do not own a BMW car (my last one was a 1995 E36) and my BMW motorcycles do not use that system either. My guess was a MAP sensor only needs a tiny hole to measure pressure (since it is static and not dynamic) and that tiny hole would not allow enough air to enter the engine. But this video is excellent to understand about Fuel Trim (I had no clue about trim)! My friends Porsche 993 is running ultra rich after having the engine out for seals, o-rings and a new dual mass flywheel and clutch. Plus we did the 964 mod to the 993 cams to pin the timing gears to the camshaft (the original 993 gear is a butt fit to the camshaft using a bolt...in my books a no-no). Anyway, I think we will have to do an ECU Drive Cycle / Readiness. Thumbs Up Dan!
13:36 Because the engine has a valvatronic system, which replaces the operation of the throttle valve, and instead of it, the valves open at a certain height, and not the throttle valve. And the typical pressure in the intake manifold is close to 950 millibars normal atmospheric pressure is 1013 millibars. Typical vacuum in most naturally aspirated engines is 300...350 millibars.
hello @DiagnoseDan , I admir your work. As a novice can I ask you a question please: Can at the idle the O2 sensor looking lean (0.1 V) and the stft and ltft still substracting fuel (-15%) or reverse the O2 sensor looking way rich and the stft and ltft adding fuel (+15%)?
Smashing video once again Dan. This test can also be used to diagnose a fuel injector fault! Running lean and both o2 sensor working ok but engine runs better adding brake cleaner means injector fault. Watching the smooth running values on these engines also helps understand the cylinders which aren't performing well, positive numbers indicate less mechanical output of the cylinder. Dont forget on most newer BMW and mini deleting codes doesn't reset the fuel trim adaptations or injector learnt values etc , so you may change faulty parts and car still runs bad with learnt values which are incorrect. Injectors for all gdi engines must be coded.
The throttle valve is used for start up and shut down other then that the valve Trinidad system varies valve lift to near 2mm at idle and controls volumetric intake during so and upon hard torque demand the lift is increased as needed
There is no vaccum in the intake because of the valvetronic sistem that controls the amout of air gettin in the cilinders by changing the lift for intake valves. Throtle body is always open and that cause no vacum in the intake
Watching this video 4 years after it came out and im amazed. Dan, thank you for setting this up and explaining all of this simple and very easy to understand!!
thanks dan for this awesome video. This video is very good at explaining wide band and narrow band 02. But my question would be this doesn't totally eliminate the possibility of the wide band is good but something causing the wideband to read rich. maybe a rare case of leaky fuel injector or a bad fuel regulator.
I have E60 M5 Autel MS908 Scanner getting bank 1 code 27C6? My problem scanner doesn't show bank 1 or 2 live data? Tried scanning another car and scanner finds them? How can I have no 02 readings? I can see 02 Temps 1&2 but nothing else? Any suggestions?
back in the 90;s a friend had a fun one. running very rich, Manual says ecm is bad change it out, Saving grace his friend had the same car they swap ,not the ecm. so the thinking outside the box happened. Hmm IF an O2 was telling an ecm incorrectly Hey I;m lean more fuel and keeps doing it the ecm obliges and you run super rich. They throw a new O2 in and instant success. Local owner had a lean issue, luckily mecanic heard of clamping off the supply line to the brake booster as well as smoke testing and yes engine soothes up instantly on clamping the hose. Pin hole from rust that started at the bottom of the canister
