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P0171 System Too Lean fixed on 2010 Prius

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by lexibothersme, May 9, 2018.

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  1. lexibothersme

    lexibothersme Junior Member

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    Thought I'd share my experience with P0171 check engine light code I've been dealing with since late March.
    I first got the CEL in late March 2018 at around 147,800 miles on my 2010 Prius. I've tried many different things, but what ultimately resolved my issue was replacing the fuel pump.

    Things I tried up until today,

    - Changing out the MAF sensor was the first thing I did on April 3rd. This was an easy 5 minute install. P0171 still occurred.
    - I had the spark plugs (NGK ILKAR7B11)and air/fuel sensor (Denso 234-9090) changed on April 14th. Still didn't resolve the issue.
    - Cleaned air intake manifold on 4/22, using NutzAboutBolts' instructional YouTube video. Took the opportunity to also change the PCV valve. While I definitely felt the car run smoother, this didn't solve the P0171 condition.
    - Changed the downstream O2 sensor on 4/29. Denso part number 234-4400. Still no luck.

    What did the trick:
    - Ordered a used fuel pump assembly (Toyota P/N 77020-47080) from Ebay that came off of a 2010 Prius with around 90,000 miles. Took a week to arrive.
    - Ordered the gasket for the fuel pump, Toyota Part Number 77169-06060. This cost $32 with tax.
    - Performed the install on 5/8, took about an hour. Test drove it for 30 miles on freeway and city, and finally got 50+ MPG again. My display shows 56 MPG. With all the previous changes (plugs, cleaning intake manifold, etc..) it ran real smooth, even better than when I first bought the car used back in 2013.

    I followed GAM's post as a guideline on fuel pump removal and installation.
    Changing a GenIII Fuel Filter | PriusChat

    I also had the Gen 3 Prius Repair Manual on PDF. Pages 3015 thru 3025 cover the fuel pump installation.
    If anyone would like the PDF, please send me a message and I'll provide you with a Google Drive link.
     
    #1 lexibothersme, May 9, 2018
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  2. lexibothersme

    lexibothersme Junior Member

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    Just wanted to add some more details to my System Lean condition. Initially, I saw my MPG drop to around 48 MPG back in Dec/Jan. I assumed it was because of the winter fuel mix. No check engine light occurred, just a drop to my MPG. I had been typically getting 50 to 52 MPG. When the CEL occurred around March, my fuel economy had dropped to around 42 MPG. At its worst, I was getting 36 to 38 MPG. What I also noticed was that city driving less than 40 MPH gave me decent (but not great) MPG. It was driving on the freeway that yielded really low MPG numbers. This led me to suspect that the my issue was related to the fuel delivery system, after having changed out the sparkplugs, MAF sensor, A/F and O2 sensors.
     
    #2 lexibothersme, May 9, 2018
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  3. NutzAboutBolts

    NutzAboutBolts Senior Member

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    Glad you got it fixed and shared your experience, I hope you kept all the old parts you replaced since they’re still good. If you’re getting a lean code, I would suspect air vacuum leak or fuel pressure. Weird how the fuel pump just crap out on you like that.
     
    #3 NutzAboutBolts, May 10, 2018
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  4. lexibothersme

    lexibothersme Junior Member

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    I thought it was a vacuum leak as well, so i had the intake manifold removed to clean as well as change the gasket. All thanks to your great instructional vid!
     
    #4 lexibothersme, May 10, 2018
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  5. NutzAboutBolts

    NutzAboutBolts Senior Member

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    Glad you got this issue fixed, it must’ve been a headache for you to go through all those parts, but now you’re an expert at this issue :)
     
    #5 NutzAboutBolts, May 10, 2018
  6. RMB

    RMB Senior Member

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    Wow! Glad to hear things worked out for you after all the parts your replaced. Adding EGR cooler cleaning (along with routine maintenance) and your Prius should run like factory new!;)
     
    #6 RMB, May 10, 2018
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  7. lexibothersme

    lexibothersme Junior Member

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    Thanks. Getting this resolved was a big relief since I have a smog check due in June. That P0171 CEL would be an instant fail.
    Hoping my post helps others that may be experiencing the same issue with the P0171 code. I found a few threads on PriusChat related to P0171, but none had a definitive resolution. In one thread, the OP ended up just selling his 2010 Prius before fixing his P0171 condition. He did everything I did short of replacing the fuel pump assembly.
     
    #7 lexibothersme, May 11, 2018
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  8. Michael Mann

    Michael Mann Active Member

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    Just completed my EGR, PCV, Manifold, Cooler cleaning along with the OCC Install and I now have the same code P0171. I suspect I have a vacuum leak from the PCV to the OCC.
     
    #8 Michael Mann, May 19, 2018
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  9. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Here's an excerpt, just the Fuel Pump replacement pages:
     

    Attached Files:

    #9 Mendel Leisk, May 19, 2018
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  10. Raytheeagle

    Raytheeagle Senior Member

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    It could be that or a gasket not seated correctly ;).

    The one on the egr to exhaust manifold can be particularly fiddly, but another one thay might be a culprit could be where the egr valve is.

    It doesn’t take much to set off the P0171 code. I’d check the gaskets for proper fitment in addition to the other disturbed connections ;).

    If the PCV hose was off, I’d bet you’d get the gross leak code set. So it’s probably a small vacuum leak.

    Good luck and keep us posted (y).
     
    #10 Raytheeagle, May 19, 2018
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  11. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Is it normally open to atmosphere, from EGR valve upstream, basically all the way back to tail pipe?

    Accordingly, I'd suspect if it's an EGR leak causing a drop in intake manifold vacuum, it would be somewhere downstream of the valve, at the EGR valve to EGR pipe, or EGR pipe to intake manifold.
     
    #11 Mendel Leisk, May 19, 2018
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  12. Raytheeagle

    Raytheeagle Senior Member

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    It’d be good to double check all work as a vacuum leak will cause the system to run lean (more unmetered air entering the process);).

    P0171 won’t just set on start up, so it could happen at any point:(.

    Look for the touched connections though(y).
     
    #12 Raytheeagle, May 19, 2018
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  13. Michael Mann

    Michael Mann Active Member

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    I ended up resecuring all my lines but I think the main culprit came from the original manifold gasket which was relatively “flat” compared to the new one I put on today. A test drive around town today and all seems good now.
     
    #13 Michael Mann, May 20, 2018
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  14. Moonlite

    Moonlite Junior Member

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    I just wanted to add that I had a similar experience with the P0171 code. I took it to a local Toyota dealer and at first, said it was a cracked intake manifold. However, the code was still present after they replaced the intake manifold and test drove it. Then they consulted a "hybrid guru" from another dealer and after a week, determined it was the fuel pump. They did not charge for the intake manifold replacement (they reinstalled the original manifold) and only charged $100 diagnostics. However, they quoted $2100 to replace the fuel pump, $1000 parts, $1100 labor. Shocked at this price I looked into installing a new pump myself. The dealer must have inflated the fuel pump quote to $2100 to recoup their losses trying to diagnose my car. I called a few nearby dealers and the fuel pump assembly #77020-47081 ranged from $480 to $590.

    I found a new factory fuel pump assembly, o-ring and shipping for $400 from McGeorge Toyota Online Part. Thanks to lexibothersme and others here, my 14-year-old son and I replaced the fuel pump in a leisurely 2 hours back in June. Immediately after replacing the pump, the P0171 code was gone and has not come back. The fuel economy has also increased by about 6-8 MPG.
     
    #14 Moonlite, Aug 18, 2018
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  15. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    @Moonlite how many miles were you at when you got the code?
     
    #15 Mendel Leisk, Aug 18, 2018
  16. Moonlite

    Moonlite Junior Member

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    The code first appeared at around 110,000 miles during a round trip a couple years back. At that time, I cleared it using a scanntool from a parts store. Several months ago and at 130,000 miles It came back and stayed
     
    #16 Moonlite, Aug 18, 2018
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  17. padroo

    padroo Senior Member

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    With all these high mileage Prii running around we don't hear much about bad fuel pumps. They hold up really well normally.

    Question, do any of thePrii have a Schrader valve for checking fuel pump pressure?
     
    #17 padroo, Aug 18, 2018
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  18. Raytheeagle

    Raytheeagle Senior Member

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    We see them here occasionally ;).

    Usually a different code is displayed (P3190?).

    I know @m.wynn has some fuel pump suspicions :whistle:.
     
    #18 Raytheeagle, Aug 18, 2018
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  19. Grit

    Grit Senior Member

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    A person posted about a dealership and 6 Prius in at one point about bad fuel pump that were to be replaced.
     
    #19 Grit, Aug 18, 2018
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  20. yeldogt

    yeldogt Active Member

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    We have two gen 3's .. one needed a fuel pump. Had over 100k on it -- Just died.
     
    #20 yeldogt, Aug 18, 2018
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