Fuel Systems: Closed Loop/Open Loop Control

[@orochimaru2010]

For those looking for answers< Open Loop> indicates a problem while means the fuel trim data is accurate and the system works at its finest.

[@ms1durfl]

Thank you so much

[@ahmadabdelwahed7042]

Does the second o2 sensor affect the performance and cause open loop?

[@orochimaru2010]

it does affect performance but doesn't cause open loop, that is caused by MAF sensor@@ahmadabdelwahed7042

[@markok0610]

​@@ahmadabdelwahed7042yes

[@marcustrue1213]

Yes because this wouldn’t communicate to the computer whether the catalytic converter is working or not

[@qazimtahir]

Gentleman your videos are really wonderful 😊😊😊😊

[@fireboy5043]

Great Info Vid Well Said and Done Learned Alot Thanks 💯 👍🏾

[@Jaden-up3bg]

Good stuff! Thank you

[@johnpaulgarrett1]

Very illuminating!

[@nickschuldt9229]

I gotta say you have explained this topic the best out of anyone over the years. Being that said I apologize for the book I'm about to write but you may be the only one who can help me and or explain it enough to me to help me figure out my problem I have been having over the years.? I have a 2006 4runner 2uzfe 4.7 L engine with 4 catalytic converters and use to have codes for all 4 o2 sensor's but now that I've replaced all 4 o2 sensor's with ome sensors I've only got one code for a p2241 now I thought it might be that it was one bad sensor so I switched sides from bank 1 to bank 2 and vice versa and still get the same code, same place but not on the other side so it's not the sensor and the scanner says in real time that the fuel system 1 or 2 I can't remember has an open loop when the other has a closed loop. Now I do have a cool air intake but if that was the problem wouldn't it affect the other o2 sensor's as well? The same hypothesis I figure goes for the heater relay and the PCM and the MAF sensor and wires from the MAF sensor would affect more than just that one o2 sensor.? Now I also hooked a multi meter to the plug and the side that works was getting 3 volts of power for the signal and the bad side that is throwing the code for p2241 is getting 9 volts of power for the signal wire. I'm guessing that one of the 2 grounds is bad and it's easy to test the all time ground but the the other one after looking at the wire diagram.....I said to myself HOLY SANTA CLAUS SH... I say that because whomever designed the 2uzfe engine are amazing at a good quality engine, they are also jokesters (I'm guessing) because when I thought I may have a starter issue I'm like oh that's easy to fix, where's the starter? Come to find out it's in the middle of the engine and hade to remove the intake manifold and coolant crossover lines ECT. So I'm thinking the designers are laughing at a run on joke that they did as a way to leave their mark and they get a chuckle out of it when they can imagine the look on the mechanics faces when they have to replace the starter. We might not find it funny but they do for one reason or another and I can see the humor in it. With that being said I have no clue how to follow how far back the PCM ground goes or better yet the places it stops off at on the way to the PCM.? Am I on the right path and is any of the o2 sensor's tied in with the same wiring with the fuel injectors or the plugs for the spark plugs and is fuel system 1 and 2 does that work the same way (analogy) as how ohms work when wiring 2 subwoofers/fuel system 1 and 2 to play at 2ohms instead of 4 ohms when coming from a one channel amplifier/gas tank. Meaning does the fuel pump, pump one line then splits off at the engine or does the fuel pump/amplifier have 2 chambers/channels in it that have two fuel lines that go to each bank/subwoofer? Not sure if that would have anything to do with the o2 sensor's but I'm not leaving out any possibility because I'm loosing my patience with this and now I'm making it my mission to know everything about my 4runner so this doesn't happen again. Thanks for your time and patience with my details and analogies and my thoughts. I would appreciate your thoughts and help and or ideas if any! Again thank you. Wwgowga

[@blissseeker9]

Great stuff. So If I am using a fuel controller which takes data from O2, modifies it to make it rich or lean, and then feeds it to PCM, then it works only in the closed loop? The higher RPM range where open loop comes into play does not get affected by this?? Much thanks

[@Bobbygale121]

Went to gm ccc school back in the eighties. Computer-controlled carburetors -- Old-timers in those days were really scratching their heads. Lots of stories of people leaving the trade "I'm a mechanic, not a rocket scientist."

[@pccastengineperformance7844]

And that was just CCC! I wonder how they would feel about a dual Gasoline Direct Injection and Port injection system with variable valve timing and lift?

[@shelbyscarforensics1878]

Jay is the Man!

[@fishinvexus]

Outboard question. On an outboard with a closed loop fuel system, I’m thinking you could add a larger throttle body and intake runner for more power. The PCM should compensate for the more air and essentially make more power? Sound right?

[@markmetaltradezz6911]

Good job thanks

[@creatorkal8416]

Excellent explanation

[@donrichardson5132]

🔥 🔥 🔥

[@Rust_valley_racing]

What happens when the cat is removed from the exhaust system ,? Am I correct that the engine will be lean across the rpm range and only have correct fueling at the highest rpm range with the closed and open loop systems

[@MaXimus666789]

My vehicle when I bought it as I understand is tuned only to run open loop as I don't even have O2 sensors, It run's perfectly fine. But the fuel economy is horrendous on idle in summer (122 ambient air temp) Will adding the O2 sensors and retuning the vehicle to closed loop. Will that improve fuel economy?

[@markjadebenitez3300]

What cause an open loop? Is there any solution to fix.?

[@jorgelopez-tt7ng]

Close loop keep closed while driving under 50 mph everything ok. but driving at 60mph or faster close loop becomes open loop if I keep out my foot of gas pedal and the system just return to close loop if speed is under 45 mph or steep on gas pedal again. Is this normal? I replaced all oxigen sensors and catalytic. And this situation persist. Any clue!

[@LC-fl3zm]

thank you im running a 2004 ls1 6.0 all stock in a 70 chevy nova its almost in the car its going to have no catalac converters what shoud i do with the second bank 02 sensors i dont thank i need them right would hp tuners delete them

[@pccastengineperformance7844]

In some applications the rear O2 sensors have a minor (well, sometimes more than minor) role in fuel trim, and then it's really for emissions purposes. For your application however, the tuner software needs to delete them since you aren't running converters. Sounds like a fun ride!

[@ariaanalvarez4229]

So thinking of like like a circuit open loop is like having an open circuit and closed loop is like having a closed circuit.

[@greenhometony]

I think other way around....

[@wmartens3806]

So what does an OL-Fault mean in a closed loop system? (from my obd2 scanner)

[@PaulHAMCO]

Open circuit. Could be a broken or nicked wire. Shorts are from fuses.

[@johndee68]

HI, not sure if you or anyone will see this, being so long ago. But I was wondering, do cars PCM's then keep going from Open Loop and Closed Loop while driving ?

[@pccastengineperformance7844]

John, my students get the "it depends" answer here. Early fuel injected vehicles would often go back into open loop at idle, under hard acceleration, if they idled too long, etc. Current vehicles with wide range air-fuel ratio sensors can stay in closed loop from a few seconds after cold start until the engine is shut off. With a wide range sensor, the computer can give a slight rich condition and stay in full control of it, allowing it to maintain closed loop operation. It can also run slightly lean during a low throttle, low load cruise condition to enhance fuel economy. Earlier "normal" oxygen sensors really can't do that (with a couple of slight exceptions!)

[@johndee68]

@@pccastengineperformance7844 Thank you for your valued and understandable reply. It saves me chasing something as possible fault when it could be just the computers inherent software management design. Yes I am referring to an Australian version 2002 Holden Commodore which has the American almost equivalent to the Buick v6 3800 series 2 motor I believe. Thanks again for taking the time to reply.

[@NORCALPYRO_]

Hi any advive would b highly appreciated. 2005 trailblazer 4.2 1 cat 2 o2 sensors. Had a po420 code 3 years ago replaced cats and o2 sensors fixed code... may 8th po420 came back changed both o2 sensors light went away 300 miles.. jun 1st Light came back on no loss in power or performance car still feels normal as its my daily driver i have noticed evertime the light comes on its after driving for a while when car is stopped at a light idling i feel a small shake like a mini mini misfire and boom light back on... pulled my freeze frame sensor 1 ol sensor 2 n/a

[@pccastengineperformance7844]

The P0420 is a code for catalyst efficiency, so anything that affects the converters ability to do its job (including simply being bad) can cause the code to set. To properly diagnose this, any other codes set besides the P0420 need to be diagnosed first (although it doesn't sound like there were any). If there are any exhaust leaks from the engine to about 12" past the end of the catalyst, those need to be fixed. Fuel trim should be checked under multiple speeds and loads, and be below 10% in all of those areas. The pre and post O2 sensors should be compared while driving down the road (disclaimer - two people for this, one driving and one watching a scan tool). At a decent load and steady throttle, such as cruising down the interstate, the pre-cat sensor (B1S1) should be very active and switching between 200-800mV, while the post catalyst (B1S2) should be steady from around 600-850mV. If the rear sensor is moving similarly to the front, the catalyst is simply not doing its job. These vehicles had ground wire issues, primarily corrosion and damaged crimps, which could lead to ignition misfires, the biggest killer of catalytic converters. If anytime in the last three years the vehicle had any misfiring cylinders, the catalyst is likely damaged. And lastly, all catalysts are not created equal; many aftermarket units do not contain the same amount of precious metals as OE units, so the require that the engine, all engine management parts, and all other emissions parts be working perfectly.

[@NORCALPYRO_]

@@pccastengineperformance7844 thanks you yes read the freeze frame s1 is ol sensor to n/a short tf is 7.0 long tf is 7.8 engine temp 210 and yes car did have a .misfire last year multiple misfire i had to chsnge 2 coils and clean the throttle body and fixed the issue... should i try cataclean or no?

[@pccastengineperformance7844]

@@NORCALPYRO_ The "Catclean" really only works to clean oil ash buildup off of the substrate. When the engine misfires it causes the cat to overheat and essentially melt down (which can be only partial). From the information provided it's going to need a new converter assembly. Although I will say at this point you wouldn't hurt anything trying the catclean. good luck!

[@NORCALPYRO_]

@@pccastengineperformance7844 thank you for your responses and information i appreciate it💪

[@jamesbroomfield7799]

What would cause your car to stay in closed loop, even during first start up of the day, cold start? My car seems to be stuck in closed loop.

[@PaulHAMCO]

That's what you want... closed loop is fine. Open loop means an open somewhere in the fuel system.

[@jesustolentino5636]

What would be the solution?

[@timchand4165]

I have a 2017 charger rt cammed it is dyno tuned on 93 no cats and straight piped . Just added high flow cats got code p1eoa Closed Loop Fueling Not Achieved Bank 2 down stream any ideas ?

[@pccastengineperformance7844]

Did it get re-tuned after the cats were installed? They have a huge affect on the readings of the downstream sensors, which I'm assuming had been tuned to work without the cats. Now that they're back on, the rear sensors are providing different information. And some manufacturers (like Chrysler) use the rear O2 sensors as well as the front for fuel trim, so changes in the gas composition (with and without converter(s)) really changes their readings.

[@timchand4165]

@@pccastengineperformance7844 no I did not retune it yet hoping that it might fix this issue since my monitor for my Downstream o2 were tuned off

[@m.b.smoshitoa8325]

But just don't understand. When you say o2 is not used at wot . Do you mean the ECU is not listening to o2 anymore. What about at half open throttle. Does it now listen. Moshitoa (south Africa

[@pccastengineperformance7844]

On older vehicles, the system tends to run slightly rich at Wide Open Throttle, so the PCM essentially ignores the O2 (unless it shows lean when it shouldn't.) Anything less than that (WOT) and the system should be using the O2 for fuel control ("listening" to it).

[@johnmwangi6291]

Sir does diesel engine us close loop to control fuel system..

[@pccastengineperformance7844]

Diesel's do not use a closed loop system like gasoline engines do. A very few run O2 sensors, but they are only for control over the exhaust emissions components. You will also find NOx (Oxides of Nitrogen) or temperature sensors in the exhaust, but those also are only for controlling the exhaust aftertreatment components. To me, the closest thing we have on a modern diesel to a closed loop system is cylinder balancing. If the Engine Control Module identifies that the crankshaft has sped up or slowed down during the power stroke of one cylinder over the others, it will increase or decrease the injection rate (delivered fuel) to that cylinder until the speed matches the other cylinders. But instead of trying to maintain a stoichiometric air-fuel ratio, it is simply trying to keep the engine's power output smooth and even. Also, a typical gasoline engine usually runs at a stoichiometric air-fuel ratio; diesels typically run very lean with respect to their stoichiometric air-fuel ratio (unless of course the owner is into "rolling coal"). Most of the fuel control for a diesel is done through load (manifold pressure, boost pressure, exhaust backpressure) and then modified if one of the exhaust aftertreatment components needs additional air for operation. There are times the Diesel Oxidation Catalyst needs additional fuel to increase its temperature, but that is done through post-injection (either cylinders injecting fuel on the exhaust stroke or a specific injector sitting in the downpipe after the turbo to spray fuel into the exhaust). Neither of these methods effects the air-fuel ratio for engine operation, only emissions control in the aftertreatment. So the short answer? Nothing like a gasoline engine!

[@johnmwangi6291]

@@pccastengineperformance7844 thank you sir... I have learned a lot from you sir..I have to read that a couple of times to get it through my head ✍️

[@bantanaarchive]

This gotta be murr bro😂

[@boogaloojuly4th]

i have 30 psi in my 1 3 5 cylinders

[@Banditt42]

congratulations

[@threadtapwhisperer5136]

Of boost pressure? Or total compression....? Cuz one way = bwaaaa sututururu Other way = aw fuck, no ring seal/valves bent or something cylinder cant seal pressure inside So... If ya didnt know, now ya do. Hopefully that wasnt compression readings, cuz that's usually not fixable without cylinder head replacements or full engine refresh.

[@boogaloojuly4th]

I ended up rebuilding the engine, still no start.

[@trishperkins5416]

What about cl fault?

[@RBPD92]

When ECU feels something bad or lazy with upstream O2 sensors or have detected misfires

[@trishperkins5416]

Thank you. This is starting to make sense to me better.

[@anthonyrstrawbridge]

I had stop within four minutes because the explanation of the oxygen sensor was incorrect. It would've been accurate to stay with lean or rich condition but instead he said, " {- Oxygen sensor sees too much oxygen - lean or too little oxygen rich"}. Why not avoid the trap and stick to what the oxygen sensor actually senses. IMO OMG! To be fair I continued listening until 4.5 minutes and gave up: This explanation and teaching is absolutely focused on misconception is absolutely confusing. I'm out - thumbs down!

[@stevenpelican7502]

This guy doesn't answer questions!

[@markjadebenitez3300]

What cause an open loop? Is there any solution to fix.?