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I have a very stubborn P0171 code

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    I have recently bought a 06 scion tc and even after installing another engine i am still seeing a p0171 code.
    I bought the car not knowing it had code problems because the seller had pulled the battery cable right before i showed up to view the car. By the time i got home the "light" was on and i was on the phone. Of course the seller claimed the light was never on before . Some people right?
    Anyway,the previous engine quit on me about a week later. I looked around and found a used motor that was running good before it was in a accident and the body was totaled. So i bought it and installed it with high hopes that the codes would leave when the old engine left. Wrong !
    The only thing i have not checked is the fuel pump pressure because i have not bought a adapter yet.
    I was wondering if it might be possible that the code cannot be erased by a regular scanner and i might have to take it to a dealer ? I know that sounds crazy but i have ran out of ideas.
    It runs fine until it warms up then the idle goes low and it starts using too much gas. The only new part i have bought was a 02 sensor,everything else i have bench tested.
    If anybody has any ideas i would really like to hear them. I have about 8 days until i have to either get it smogged and finish getting it registered or put it on non-op until i get it figured out.It will not pass smog with the C.E.L. on.
    There are are two other code's that wont clear also which are c0215 and c0210 . Right and left rear speed sensors. I am not really worried about these as much as i am as the p0171. The fact is i have a feeling that the previous motor was damaged because the owner drove it too long with the p0171 code. Running a engine when it has a lean condition is very bad on a motor.
    I will go for now. Thanking you in advance for any help you may offer.
    Thanks MRLUV! excellent info you posted up.

    To the original poster, think of what you transferred over to the new engine, that will give you a short list of what the problem is. Since you're having the same exact CEL code.
    • Edited 1 times, last by sciontc_mich on .
    Your other post has been merged into this thread..

    cap10hunt wrote:
    I have a Actron Autoscanner Plus and i am sure that if i was smart enough to understand what it is telling me i could figure out what in the heck is wrong with my 2006 scion TC. Hope somebody can steer me in the right direction.
    What i would like help understanding is the "short term and long term" fuel use ?
    I am viewing the freeze frame data after a P0171 code was set and most all of the other info is pretty straight forward but i am having a devil of a time trying to wrap my head around the fuel data.
    Is there anybody out there who could break it down for me and make it a little bit easier for me to understand?
    The numbers that are showing for the freeze frame that set the code are "short term" is 3.1 and "long term" is 38.3 I am pretty sure that somehow i might be able to tell if the fuel pump is bad ???? Heck..... I dont know...
    • Edited 1 times, last by sciontc_mich on .
    sciontc_mich wrote:
    cap10hunt wrote:
    I have a Actron Autoscanner Plus and i am sure that if i was smart enough to understand what it is telling me i could figure out what in the heck is wrong with my 2006 scion TC. Hope somebody can steer me in the right direction.
    What i would like help understanding is the "short term and long term" fuel use ?
    I am viewing the freeze frame data after a P0171 code was set and most all of the other info is pretty straight forward but i am having a devil of a time trying to wrap my head around the fuel data.
    Is there anybody out there who could break it down for me and make it a little bit easier for me to understand?
    The numbers that are showing for the freeze frame that set the code are "short term" is 3.1 and "long term" is 38.3 I am pretty sure that somehow i might be able to tell if the fuel pump is bad ???? Heck..... I dont know...



    I have merged both thread into one.. so on we go..

    Yes the ltft (long term fuel trim) is cumulative based on the stft (short term fuel trim). Your numbers are way out of specification. Usually the normal is +/- 10% for both. The ltft number of 38.3 you have is showing that there is a long term issue, and MRLUV did post the causes for the p0171 code you're getting. Something went bad, the ECU (computer) is compensating for it, once it got outside the normal percentages it illuminated the CEL.

    The only way to know what is causing this is by testing everything in the list for p0171. Please look at the list he posted, that is what causes the code.

    To help you understand, here's some good info I found. Help ya understand st and lt fuel trims..

    https://www.obd-codes.com/faq/fuel-trims.php

    edit: another link.. some explanations too
    https://www.obd-codes.com/p0171
    • Edited 1 times, last by sciontc_mich on .
    also.. looking at that p0171 code list. Makes me wonder if your injectors are dirty. A cheap/simple thing to try is pour a can of BG Products 44k fuel cleaner into the gas tank, fill up the tank so it mixes the cleaner, run that through. See if your fuel trims change after that. It's about $20 a can. The reason I suggest this is because it has cleared up issues for me before. Not the numbers of fuel trims you're getting but for $20 might as well try.

    here's a can of it on amazon

    https://www.amazon.com/BG...p;s=automotive&sr=1-2

    I gave you the link for the plastic bottle, less to be smashed in shipping!

    EDIT: also.. get a can of CRC MAF air flow sensor cleaner from autozone or oreilly, whoever is cheaper. Take the MAF sensor out (car off, ignition off) and clean it with a gentle spray of the MAF sensor cleaner. If you look down the tube with a bright flash light you'll see what looks like two fine wire probes, almost like dental floss. That's the sensor. The amber bulb on the outside is the idle air temp sensor. Clean both, let dry, reinstall. Try those two things. I've actually gotten poor gas mileage and rough idle (a lot of us have) and it's all due to a dirty MAF sensor.
    Hello,
    Just to keep my post updated..... I finally cleared the "wheel sensor" codes. It was caused when the previous owner installed a radio/video unit.I guess the player has to be tied into the wheel sensor to make sure that the video function is not used while the car is moving forward ?? Anyway,the code went away as soon as i took the unit out. I guess i am going to leave it out until i figure out the P0171.....
    I have cleaned the maf,replaced the front 02 sensor,changed the injectors,installed a new intake gasket,tested the fuel pressure,replaced or checked all the vac lines,and put a set of new plugs in. No luck so far...... Its getting harder to start for some reason also.
    I ran the car with my code reader connected and it showed that one 02 sensor is putting out almost 4 volts !! The other one is about .450 if i remember right. Am i reading this right or do i have a bad ecu? I ran it twice to make sure and both times one sensor is generating close to 4 volts. ????
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