How would some of those root causes effect only 1 bank & not the other though? Like MAF, or fuel filter/pump/pressure, or vacuum leaks. Wouldn't those effect both banks if your car really has 2 banks?
Good gawd, I went to autozone to see their prices on renting a fuel pressure gauge kit... $150 bruh... I just ended up buying one for $30 bucks... insane world we live in.
I went to the dealership because my Toyota Corolla 2010 shows P0171 code and VSC is off is blinking nonstop in my dashboard. They said it was because of my fuel pump and it needs to be replaced.
Update: after cleaning the very dirty MAF sensor and reseting it by running it almost 50 miles the check engine sign still came up same code P0171 😢 dont know what to try next.. im thinking fuel filter...
07 Corolla with this code so I replaced Upstream 02 Sensor, replaced MAF Sensor, checked fuel pump pressure, replace PCV Valve, smoked tested intake and found no leaks. Haven't replaced or checked fuel injectors yet, but I vacuum tested the Vapor Canister Purge Valve and it wouldn't hold pressure. I ordered the part and will update if that fixes the problem. My cars symptoms where terrible fuel economy, rough idle, hesitation and hard starting. I hope this helps others.
@bishop2355, thanks for the head's up about the vapor canister purge valve. In my case, a couple vacuum lines were swapped and I was getting vacuum flow through the air filter housing straight past the throttle butterfly. After reviewing the 1ZZ-FE vacuum hose routing diagram, it was obvious two hoses were swapped, and the fix took 1-minute. Like you, I had already replaced the O2 sensor, replaced the MAF Sensor, checked fuel pump pressure, replaced PCV valve, smoke tested the intake (twice) and replaced the inlet manifold gasket, serviced the fuel injectors and replaced their soft goods. Oh my, vacuum hose routing. . . . Oh well, it's good to have new stuff in the engine to ensure it runs well into the future 🙃
Smoke out that intake manifold you will find that vacuum leak, I smoke out my intake manifold the vacuum leak was coming out of my IAC valve that sit above the tps sensor, did you know a pcv can throw a lean code just check your filler cap if you see condensation or white milky stuff on the cap the pcv valve is bad, it either stuck open or close
Did you have very high LTFT? The LTFT in my 2000 Corolla goes up to 39% so it triggers the P0171 code. I have changed the fuel cap, PCV valve, 02 sensor, MAF sensor, and air intake gasket. I am planning to change the car's ECU next but this IAC valve is intriguing as the potential cause. I did spray soap and water under the hood the other day looking for vacuum leaks and didn't get any reactions, however.
I found 99% of the time it is 2014-2020 Toyota Vacuum Valve. I own 14 Toyota Corolla 2017 and 2018 in the fleet and new Toyota Vacuum Valve has fixed problem
Hi HVAC, I worked on a neighbor's 2002 Camry 2.4L with this code. Installed new plugs, new coils, new air filter, cleaned the MAF sensor, and installed a new Denso O2 sensor. The car has 140k miles, so I figured these would need replacement anyway just due to age. The check engine light did go off by itself for a while, but then my neighbor reported that the light came on again. Could this be a fuel delivery issue then?
I took my 2006 Toyota Corolla to my mechanic very trusted mechanic by the way. This code he was not able to figure out because pretty much everything was working well. He made sure that everything was ruled out, but he said that he just cleaned fuel injectors, as well as the anything else needed to be cleaned. The check engine light turns back on and it’s the same code so I’m not sure what to do.
One significant "Vacuum Leak" possibility is if you get your vacuum hoses crossed. I just found on my 2004 Corolla that a vacuum line was connected to the air filter housing and going to the throttle body downstream of the butterfly. BAD DEAL. So, make sure the carbon canister evap system is plumbed to the throttle body. With the wrong routing, your Long Term Fuel Trim will constantly stay high as the car tries to adjust, and your MAF sensor will read LOW since the vacuum line is bypassing the MAF and throttle. Many thanks to @bishop2355 for getting me to focus on how the evap system works, rather than just trusting that everything is lined-up properly from the repair shop.
I been dealing with this for a year already it's driving me crazy, replaced maf, o2 sensor, coolant temp sensor, pcv valve, pcv hose, smoke the engine 5 times already, replaced the fuel pump with oem, new plugs, fuel injectors are within resistance specs, purge valve working properly, and the code p0171 still showing up, the car runs just fine nothing crazy like stalling, miss firing or some of that nature, the vehicle stars right away with no issues, mine is a 2007 corolla and I don't know what else to do. Fuel trims are stft is between -9 to 7 and ltft stays at 33.6 at idle and spikes up as soon as I press the gas pedal
I have a 2013 frs and out of no where it turned off on me on the highway. a month or 2 it started to start 2-3 seconds after ignition but it was rare. A week before my car turned off, there was a slight knocking/tapping noise after 80mph that sounded like it was infront of the driver side. I had it scanned and the only thing that came up was the P0171 code. I changed the tank fuel pump thinking it gave out and it did not work. I took out the hpfp (did not take out the part holding/under the hpfp) and the coil looks good, so did the roller so i didnt think much of it but Im thinking it could be it considering the slight knocking noise at a higher rpm/mph, it being heard infront of the driver side and not knowing if the problem could be inside the hpfp. It has been such a headache because i still havent found the problem (I tried checking the fuel pressure on the lines but it is so difficult to install, and also the fittings i rented are not capable for the 3 fuel lines on top of the injectors. I did however check the middle fuel line which i think is the out and it had 0 psi)
Hi there! 1998 toyota corolla, it sputters in the beginning but tuns fine after, and I already replaced the o2 sensor, by chance do you thinko it would be the injector?
A mechanic at Toyota told my wife the charcoal canister was bad because the hose came off, said it needed a new one for 700 dollars. Does this sound possible? I replaced the hose and it's been fine.
@@markjacoby2414 Not necessarily. I've been trying to solve this P0171 issue for three years on my 2000 Corolla. A mechanic believes it is the car's ECU as the car drives fine.
Mine had the code and stalled from time to time and even turned off a few times till one day it just didn't turn on anymore. I changed the fuel pump and it started right back up
I have a 2019 Toyota Camry I keep getting this code!!!! I’ve cleaned MAF and throttle worked fine then got the code again so I replaced the sensor completely. I cleared the computer was working fine for a day and just got the code again this morning. Please lmk what to do 😭
This is happening now in 2024 on a 2010 Yaris. Same exact codes running horrible 40 miles per hour only limp mode you name it. Already replaced all the parts so I'm already out some dough. I'll have to try this
Hey buddy thanks for all this information, I have a question : are all these steps the same for a newer like on a 2020 toyota corolla? I mean for example gas filters could be skipped?
@@HVAC_Mechanicthanks for your help, I have 2020 corolla, i had replaced all what you mentioned and the check engine still on after over 20 miles the code says mass airflow sensor but has been replaced it from the dealership, any idea please?
2000 Avalon XL P0171 code. I went to Denso's website for O2 sensor part#, and also saw it listed an A/F sensor. Which would be the one to change to try to clear the code. I understand that the problem may not be one or the other sensor. Thanks for replying.
The front one being the sensor next to the radiator? I was under the car to see how hard it would be to access the upstream sensor near the firewall (looks like a pain in the butt) and I assume there is another just b4 the cat converter. So is there a total of 3 or 4 sensors (2 upstream and 2 downstream?@@LA_Commander
I need help. Have a 2013 Corolla with this code. Been experiencing rough idle and intermittent stalling. Took it to Toyota 3 times and they checked all of these things and found nothing wrong . Simply said everything was within specs and they couldn’t duplicate the problem and just cleared the code off the computer. Car cutoff in the middle of an intersection today with this same code . Please help
@@indiejones4683 Did they check everything? I mean not only the fuel pump but also the fuel filter, the fuel lines, the fuel injectors, and the fuel pressure regulator?
@@indiejones4683 Wow, that really sucks man. If it's not a fuel issue then it sounds like some kind of a vacuum leak somewhere. Air is entering the system and not being properly metered, causing a bad idle and engine cutout. If your mass airflow sensor ok? Any vacuum leaks or air intake leaks>
In my case I did find that one of the hoses going to my airbox had a leak in it. After I fixed it however the check engine light was still on. Is there a recommended drive period for the system to recognize the leak is no longer there?
@@repoman6034 got it back from the shop they couldn’t figure it out, fuel pressure was good. Only charged 20 bucks instead of the $90 which made me grateful. Got home, thought long and hard for a day… “ let me return the aftermarket MAF to AutoZone and get the Denso”.SOB!!! light hasn’t came on since. Well at least I got some new stuff put on my car lol. “face palm”
The MAF sensor Grams/Second (g/s) should show zero or close to it when the engine is not running. With the engine running double the RPM, and the Grams/Second should also double. Here is video. ua-cam.com/video/kzISHRN1Qjs/v-deo.html
How would some of those root causes effect only 1 bank & not the other though?
Like MAF, or fuel filter/pump/pressure, or vacuum leaks. Wouldn't those effect both banks if your car really has 2 banks?
Good gawd, I went to autozone to see their prices on renting a fuel pressure gauge kit... $150 bruh... I just ended up buying one for $30 bucks... insane world we live in.
They usually loan it to you with a deposit of the tool value. You get it back when you return it.
150 is the cost of the tool, you get that back when you return it. Its a literal tool loaner program......
You get the money back when you return it. It's a deterrent for you to keep it.
Bruh . You is smart 😂😂
@@f4s1a1k9a5p Yes, I just quit after 15 months because I'm moving. Lots of loaner tools.
I went to the dealership because my Toyota Corolla 2010 shows P0171 code and VSC is off is blinking nonstop in my dashboard. They said it was because of my fuel pump and it needs to be replaced.
I Have a dirty maf sensor will try n clean it today. Lol since i started with first o2 sensor n didnt do it i jumped the gun on it. Great video btw.🙏
Update: after cleaning the very dirty MAF sensor and reseting it by running it almost 50 miles the check engine sign still came up same code P0171 😢 dont know what to try next.. im thinking fuel filter...
another question, is there anyway to narrow down if its the filter causing problem as opposed to having to check fuel pump pressure.
@@sudipb7467no still trying to working on 😅
@@sudipb7467 fuel filter replaced, nothing. Mechanic says rumbling in Catalytic Converter seems to be the issue. Need a new Cat i think
@@syfodias-jedimasterUpdates a month later?
07 Corolla with this code so I replaced Upstream 02 Sensor, replaced MAF Sensor, checked fuel pump pressure, replace PCV Valve, smoked tested intake and found no leaks. Haven't replaced or checked fuel injectors yet, but I vacuum tested the Vapor Canister Purge Valve and it wouldn't hold pressure. I ordered the part and will update if that fixes the problem. My cars symptoms where terrible fuel economy, rough idle, hesitation and hard starting. I hope this helps others.
Did that solve your P0171 code, and if so, any understanding why you didn't have a P0441 Incorrect Purge Flow code?
@bishop2355, thanks for the head's up about the vapor canister purge valve. In my case, a couple vacuum lines were swapped and I was getting vacuum flow through the air filter housing straight past the throttle butterfly. After reviewing the 1ZZ-FE vacuum hose routing diagram, it was obvious two hoses were swapped, and the fix took 1-minute. Like you, I had already replaced the O2 sensor, replaced the MAF Sensor, checked fuel pump pressure, replaced PCV valve, smoke tested the intake (twice) and replaced the inlet manifold gasket, serviced the fuel injectors and replaced their soft goods. Oh my, vacuum hose routing. . . . Oh well, it's good to have new stuff in the engine to ensure it runs well into the future 🙃
any update?
Smoke out that intake manifold you will find that vacuum leak, I smoke out my intake manifold the vacuum leak was coming out of my IAC valve that sit above the tps sensor, did you know a pcv can throw a lean code just check your filler cap if you see condensation or white milky stuff on the cap the pcv valve is bad, it either stuck open or close
Did you have very high LTFT? The LTFT in my 2000 Corolla goes up to 39% so it triggers the P0171 code. I have changed the fuel cap, PCV valve, 02 sensor, MAF sensor, and air intake gasket. I am planning to change the car's ECU next but this IAC valve is intriguing as the potential cause. I did spray soap and water under the hood the other day looking for vacuum leaks and didn't get any reactions, however.
I found 99% of the time it is 2014-2020 Toyota Vacuum Valve. I own 14 Toyota Corolla 2017 and 2018 in the fleet and new Toyota Vacuum Valve has fixed problem
Hi HVAC, I worked on a neighbor's 2002 Camry 2.4L with this code. Installed new plugs, new coils, new air filter, cleaned the MAF sensor, and installed a new Denso O2 sensor. The car has 140k miles, so I figured these would need replacement anyway just due to age. The check engine light did go off by itself for a while, but then my neighbor reported that the light came on again. Could this be a fuel delivery issue then?
Get a OEM sensor, not the Denso brand.
@@c.p.5741 that is the OEM for this car
@@c.p.5741I don't mean to be contradictory, but isn't Denso the OEM for Toyota? I've read on Toyota forums that only Denso will function correctly.
Denso is OEM...
Or bad gas from the gas pump.
I took my 2006 Toyota Corolla to my mechanic very trusted mechanic by the way. This code he was not able to figure out because pretty much everything was working well. He made sure that everything was ruled out, but he said that he just cleaned fuel injectors, as well as the anything else needed to be cleaned. The check engine light turns back on and it’s the same code so I’m not sure what to do.
One significant "Vacuum Leak" possibility is if you get your vacuum hoses crossed. I just found on my 2004 Corolla that a vacuum line was connected to the air filter housing and going to the throttle body downstream of the butterfly. BAD DEAL. So, make sure the carbon canister evap system is plumbed to the throttle body. With the wrong routing, your Long Term Fuel Trim will constantly stay high as the car tries to adjust, and your MAF sensor will read LOW since the vacuum line is bypassing the MAF and throttle. Many thanks to @bishop2355 for getting me to focus on how the evap system works, rather than just trusting that everything is lined-up properly from the repair shop.
Thanks for the video. Cleaned my MAF with brake cleaner. Code disappeared :-)
Very concise and informative. Thank you
I been dealing with this for a year already it's driving me crazy, replaced maf, o2 sensor, coolant temp sensor, pcv valve, pcv hose, smoke the engine 5 times already, replaced the fuel pump with oem, new plugs, fuel injectors are within resistance specs, purge valve working properly, and the code p0171 still showing up, the car runs just fine nothing crazy like stalling, miss firing or some of that nature, the vehicle stars right away with no issues, mine is a 2007 corolla and I don't know what else to do. Fuel trims are stft is between -9 to 7 and ltft stays at 33.6 at idle and spikes up as soon as I press the gas pedal
I have a 2013 frs and out of no where it turned off on me on the highway. a month or 2 it started to start 2-3
seconds after ignition but it was rare. A week before my car turned off, there was a slight knocking/tapping noise after 80mph that sounded like it was infront of the driver side. I had it scanned and the only thing that came up was the P0171 code. I changed the tank fuel pump thinking it gave out and it did not work. I took out the hpfp (did not take out the part holding/under the hpfp) and the coil looks good, so did the roller so i didnt think much of it but Im thinking it could be it considering the slight knocking noise at a higher rpm/mph, it being heard infront of the driver side and not knowing if the problem could be inside the hpfp. It has been such a headache because i still havent found the problem (I tried checking the fuel pressure on the lines but it is so difficult to install, and also the fittings i rented are not capable for the 3 fuel lines on top of the injectors.
I did however check the middle fuel line which i think is the out and it had 0 psi)
Hi there! 1998 toyota corolla, it sputters in the beginning but tuns fine after, and I already replaced the o2 sensor, by chance do you thinko it would be the injector?
A mechanic at Toyota told my wife the charcoal canister was bad because the hose came off, said it needed a new one for 700 dollars. Does this sound possible? I replaced the hose and it's been fine.
The crazy part of p0171 is that my car drives just fine!!
It's an emissions code, not necessarily a bad driveability issue
Mine starts on the second crank when the car has been sitting for a while but it drives fine.
Yeah, but if you keep driving it, it will destroy the catalytic converter
@@markjacoby2414 Not necessarily. I've been trying to solve this P0171 issue for three years on my 2000 Corolla. A mechanic believes it is the car's ECU as the car drives fine.
tre - I work in a parts house. When someone wants the OBD2 tested, I always ask how is it running. Almost always, car is running fine.
Mine had the code and stalled from time to time and even turned off a few times till one day it just didn't turn on anymore. I changed the fuel pump and it started right back up
Awesome video appreciated.👍
I have a 2019 Toyota Camry I keep getting this code!!!! I’ve cleaned MAF and throttle worked fine then got the code again so I replaced the sensor completely. I cleared the computer was working fine for a day and just got the code again this morning. Please lmk what to do 😭
This is happening now in 2024 on a 2010 Yaris. Same exact codes running horrible 40 miles per hour only limp mode you name it. Already replaced all the parts so I'm already out some dough. I'll have to try this
Will engine even run with maf unplugged?
It depends on the vehicle; some won't run or have issues, while others use the MAP (Manifold Absolute Pressure) Sensor to keep running.
Hey buddy thanks for all this information, I have a question : are all these steps the same for a newer like on a 2020 toyota corolla?
I mean for example gas filters could be skipped?
Yours doesn't have the fuel pressure regulator, but all else should be the same. The fuel filter is located in the gas tank in the fuel pump.
@@HVAC_Mechanicthanks for your help, I have 2020 corolla, i had replaced all what you mentioned and the check engine still on after over 20 miles the code says mass airflow sensor but has been replaced it from the dealership, any idea please?
i Have a 2001 Toyota Solara and it was the Brake booster
I have Toyota corral 2016 every time I fill up my gas tank my vehicle were not started my car what will be the problem
That is a common symptom of a bad vent valve in the charcoal canister. It should give an EVAP code though.
Perfect short video
Can you please advise on what is the appropriate pressure for 2008 Corolla
2000 Avalon XL P0171 code. I went to Denso's website for O2 sensor part#, and also saw it listed an A/F sensor. Which would be the one to change to try to clear the code. I understand that the problem may not be one or the other sensor. Thanks for replying.
If you're going to replace the O2 sensor, replace the front one. That is the air fuel ratio sensor.
The front one being the sensor next to the radiator? I was under the car to see how hard it would be to access the upstream sensor near the firewall (looks like a pain in the butt) and I assume there is another just b4 the cat converter. So is there a total of 3 or 4 sensors (2 upstream and 2 downstream?@@LA_Commander
@@fabfabber yes, the one in front. Should be fairly easy to replace
I need help. Have a 2013 Corolla with this code. Been experiencing rough idle and intermittent stalling. Took it to Toyota 3 times and they checked all of these things and found nothing wrong . Simply said everything was within specs and they couldn’t duplicate the problem and just cleared the code off the computer. Car cutoff in the middle of an intersection today with this same code . Please help
Sounds like a bad fuel pump or fuel delivery issue
@@LA_Commander they said they checked it and it was fine
@@indiejones4683 Did they check everything? I mean not only the fuel pump but also the fuel filter, the fuel lines, the fuel injectors, and the fuel pressure regulator?
@@LA_Commander they said they did. I specifically requested it the last time I took my car there after I did research on my own.
@@indiejones4683 Wow, that really sucks man. If it's not a fuel issue then it sounds like some kind of a vacuum leak somewhere. Air is entering the system and not being properly metered, causing a bad idle and engine cutout. If your mass airflow sensor ok? Any vacuum leaks or air intake leaks>
My 03 ls 430 MAF reading 0.65 while Engine off is that normal
If they are reading a high number when the engine is off, and there is no wind blowing, then usually, they are bad or dirty and need to be cleaned.
What year toyota?
i bring to shop to changed pcv (oem) 2014 i4 camry got this code y online happen in idle in 75mph long term fuel is 8% good when idle 28% long term
In my case I did find that one of the hoses going to my airbox had a leak in it. After I fixed it however the check engine light was still on. Is there a recommended drive period for the system to recognize the leak is no longer there?
Personally i would clear the code with a OBDII reader and then drive normally. If the engine light doesn't come back on than you solved it!
You could have multiple leaks, too.
I’m so lost.
New items:
MAF, upstream o2, pcv valve, intake manifold gasket, valve cover gasket, cleaned all injectors. Still with the same code 😢
Time to check your fuel pressure.
@@repoman6034 got it back from the shop they couldn’t figure it out, fuel pressure was good. Only charged 20 bucks instead of the $90 which made me grateful. Got home, thought long and hard for a day… “ let me return the aftermarket MAF to AutoZone and get the Denso”.SOB!!! light hasn’t came on since. Well at least I got some new stuff put on my car lol. “face palm”
Figured it out?
@@jeremiahderousselle8044 yep, i cheaped out and bought a low end MAF. Went OEM and it’s good 👍🏼
@@RandomVids-hx1pymy local shop is ass also smh an I have a smog coming, they talking about it’s the spark plugs and ignition coils
Thanks for posting.. what if you have a reading of 0.00 on your MAF SENSOR! on live data,?
The MAF sensor Grams/Second (g/s) should show zero or close to it when the engine is not running. With the engine running double the RPM, and the Grams/Second should also double. Here is video. ua-cam.com/video/kzISHRN1Qjs/v-deo.html
@@HVAC_Mechanic
Thanks you gained a new subscriber!
👍👍👋👋