Question about 2001 Toyota Corolla

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2000 Toyota Corolla P0171

Got a P0171 trouble code today. I purchased a reader a long time ago but never had to use it until now. That is why I got a Toyota! :) Here is my freeze data. Hope maybe someone can tell me what it indicates. Speed 59mph Intake Air 100F Lift Bank 1 21.8% 3324 RPM Calculated Load 49.8% Engine Coolant 188F STFT Bank 1 18.7% Fuel System 1 Closed Loop Thanks for you help.

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  • Jonathan Jun 01, 2009

    Thank you rjbeg123, I will clean it tomorrow when it is light out and report back.

  • Jonathan Jun 01, 2009

    rjbeg123, thanks for your help. I cleaned the MAF sensor. It was not real bad but did have a nice coating of grim on the sensor tip and wires.

    Looks like I might be able to pull out in front of traffic again! I mean it is not fast by any means but at least it is not coming to a stop almost like it was before.

    Thanks again.

  • Jonathan Jun 02, 2009

    Does it only record the freeze data if there is a problem? I don't know how to view the data if it does not create a trouble code.

    I checked the air filter and it looks good. I replaced it not long ago. But I think it might be time to change the spark plugs? They are original with over 100,000 miles.

    My code reader is a INNOVA 3110.

  • Jonathan Jun 02, 2009

    It looks like I would need to force it to create a trouble code to read the freeze data. And my model will only show the freeze data from the highest priority trouble code. But I only paid around a $100 for it if I remember correctly. So I guess I need to find a way to create a code but still let the car run OK or just wait and see if I get a pending or trouble code.

  • Jonathan Jun 02, 2009

    Sounds good, I don't like to fix what is not broken. But from what I can tell it should be fine. She is running much better after cleaning the MAF. No more pause in the middle of the road when I am pulling out from a stop. I always had to turn the A/C off before to be safe but now it seems OK when it is not. The car is also starting up faster.



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When the fuel trim is high teens or in the 20s then its the MAF that the problem. If fuel trim is normal, 2-5 then its the O2 sensor.

Buy "Electrickleen" at the parts store.
Remove the MAF sensor, WHILE COLD, and blast the wire inside with cleaner.
The "hotwire" gets gummed up and changes the resistance of the wire so you get a bad input to the ecu and it trys to lean out for a rich condition that doesnt exsist.When it cant adjust anymore it trips the po171 code.

Posted on Jun 01, 2009

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  • rjbeg123 Jun 01, 2009

    Glad I could help you might want to check the freeze data again and see where your fuel trim is coming in now. Remember your MAF sensor is all about airflow too so make sure you have a clean air filter and your intake is unobstructed and clean.

  • rjbeg123 Jun 02, 2009

    Not sure if the Inova does, I have a snap-on reader that has a freeze data button that I can push while the car is running and pull up the data on fuel flow. It's a nice feature.

  • rjbeg123 Jun 02, 2009

    If it's running OK let it go! You'd have to force a fuel issue code anyway so your freeze data wouldn't be valid anyway. Glad I could help!



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