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P0171 at full throttle

Discussion in 'Generation 1 Prius Discussion' started by mlibanio, Aug 15, 2011.

  1. mlibanio

    mlibanio Member

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    Hi everyone, I have a 2002 prius with 130,000 miles on her, and so far so good except for a small problem for the last three months, I get an intermittent P0171 code. I know it means Lean Condition in Bank 1. However, I can run the car for weeks without it coming on. If I go full throttle getting onto the highway for example it may come on, but even then its not all the time. Not sure why only full throttle. But if I drive her gently, I will never see the CEL at all. Any idea's? I may pull off the spark plugs to check tomorrow. Fuel economy is around the usual for me at 46-49 mpg with average speeds of 75-85 mph. I don't think its vacuum related, but I will entertain any diagnostic suggestions and report back.

    Thanks.

    P.S. Even when the light comes on, there are no driveability issues, and the car behaves totally normally. Even at sustained speeds of 85-90 mph, the light will not come, so I am assuming its load related and not fuel system related.
     
    #1 mlibanio, Aug 15, 2011
  2. seilerts

    seilerts Battery Curmudgeon

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    Clean (first) or replace (next) the MAF sensor. 99% of the time this is the problem for this particular code.
     
    #2 seilerts, Aug 15, 2011
    yotatoter likes this.
  3. Ffejrobins30

    Ffejrobins30 New Member

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    P0171 at WOT is very indicative of a faulty MAF sensor. High fuel trims(lean conditions) in high RPM is MAF, High fuel trims at low RPM is vacuum leak.
     
    #3 Ffejrobins30, Aug 15, 2011
  4. mlibanio

    mlibanio Member

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    Hi guys that is what I thought. Toyota here is charging $281 + tax. Oh well, gotta do it! I may look at purchasing one in the US instead of here in Toronto. Are there any aftermarket alternatives?
    Thanks.
     
    #4 mlibanio, Aug 18, 2011
  5. seilerts

    seilerts Battery Curmudgeon

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    Did you try cleaning it yourself? It is easy, just need a Phillips screwdriver and a can of CRC MAF sensor cleaner.
     
    #5 seilerts, Aug 18, 2011
  6. ea8631

    ea8631 Member

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    like he said you can clean it yourself or you can get it from US and replace yourself. P/N is 22204-21010 and it cost around US$133.
     
    #6 ea8631, Aug 18, 2011
  7. bobofky

    bobofky Member

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    I am having problems with the check engine light showing P0171. Did you solve your problem? Mine appears to be with the ECM. I replaced it with a used one from XVipers Inc. and it appears to be defective. I am not having any success at contacting XVipers inc.
     
    #7 bobofky, Dec 19, 2011
  8. seilerts

    seilerts Battery Curmudgeon

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    What makes you think it is the ECM?

    Keep trying XVipers by phone. Reviews of them have been mixed. People that visit the yard in person have been generally pleased, however.
     
    #8 seilerts, Dec 19, 2011
  9. bobofky

    bobofky Member

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    I am having the same problem with P0171. Replaced catalytic converter. Replaced upstream O2 sensor. Replaced ECM with a used one from XViper. It did not send voltage to the downstream O2 sensor. Replaced ECM with a reconditioned one from Auto Comp. Replaced the downstream O2 sensor so that we wouldn't have to get in there again. Now getting P3091 and suspect MAF sensor and/or Throttle Body.
     
    #9 bobofky, Dec 23, 2011
  10. tnt01prius

    tnt01prius Member

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    Did you finally solve this puzzle? I've got P130 and P0171. Only got those after replacing the front exhaust for P1436. MAF sensor has been cleaned. Too many variables. I'm thinking about spending $90. for diagnostics at a local import garage to hopefully pin-point the problem. Any more suggestions?

    Update. Though P130 indicated #1 O2 Sensor, actually new Denso MAF Sensor eliminated the DTCs all together. Also, I removed the K&N air filter (installed in 2005 and reconditioned as needed). I had issues with MAF sensor before (cleaning took care of it then).
     
    #10 tnt01prius, Mar 13, 2014
  11. JOE-PHBR-San.Antonio

    JOE-PHBR-San.Antonio Junior Member

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    Very Good Job! I was about to Say Clean The MAF Sensor First before you go for part replacement!
    We have seen " P0171 " several time when we go for any Prius hybrid battery battery installations,and cleaning the MAF Sensor fixes the problems most of the times!
    Glad you got it fixed!
     
    #11 JOE-PHBR-San.Antonio, May 27, 2014
    Last edited: May 27, 2014
  12. C Clay

    C Clay Member

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    Would the readers of the forum think the eBay MAF sensors are adequate. What makes them fail anyway?
     
    #12 C Clay, Jul 22, 2014
  13. tnt01prius

    tnt01prius Member

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    I purchased a DENSO 197-6020 Mass Air Flow Sensor from myautopartswholesale on ebay for $74.68 and "free" shipping and it took care of P0171.
     
    #13 tnt01prius, Jul 22, 2014
  14. waynedubjay

    waynedubjay Junior Member

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    Got p01717 and p3190, ran out of fuel had one last bar non blinking left . I usually have 15 miles after it blinks.
     
    #14 waynedubjay, Mar 23, 2016
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