P0171 System Too Lean (Bank 1)
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This is a discussion on P0171 System Too Lean (Bank 1) within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; I have done a lot of searching for help on this error code, but most topics point back to some ...

  1. #1
    Supporting Member mjboudreaux77's Avatar
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    P0171 System Too Lean (Bank 1)

    I have done a lot of searching for help on this error code, but most topics point back to some sort of aftermarket intake being the culprit.

    I had a Stage 1 Cobb AP map, and a K&N air filter. Car has run awesome until just this past Monday. It started bucking really bad at low speed (in the parking garage), and turned into more of a hesitation when I got on the highway. Sure enough, the CEL turned on and I read out the "P0171 System Too Lean (Bank 1)" code.

    I immediately took the K&N filter out and replaced with a standard one (I know this wasn't the culprit), and also un-installed the accessport so I could return to stock settings. This didn't help. The car feels like it is going to stall at idle.

    I filled up with gas the night before all of this happened, but I have never had problems with this particular station before. I have now put some dry gas in the car, and topp'd off with 93 octane from another station.

    Any ideas?
    If I don't die by Thursday, I'll be roarin Friday night - Jimmy Buffett

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  3. #2
    Registered User EvoEatr's Avatar
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    Have you checked all intake clamps and vacuum lines and made sure none are disconnected or damaged? You mentioned the car is back to stock now? How many miles are on the car? What happens if you clear the code? does it come back on immediately?

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    Supporting Member mjboudreaux77's Avatar
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    Quote Originally Posted by EvoEatr View Post
    Have you checked all intake clamps and vacuum lines and made sure none are disconnected or damaged? You mentioned the car is back to stock now? How many miles are on the car? What happens if you clear the code? does it come back on immediately?
    Clamps all look good, can't see any hose problems.

    I cleared the code, and within 15 miles of driving, the light came back on.

    The bucking, hesitation, and rough idling seem to go from bad to worse to bad... It doesn't go away, but it seems to change how violent it is.
    If I don't die by Thursday, I'll be roarin Friday night - Jimmy Buffett

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    Registered User EvoEatr's Avatar
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    Well If your 100% sure the exhaust and intake system have no leaks and all lines look properly connected and not damaged I would prob be checking fuel pressure, the coolant temp sensor, and the intake air temp sensor..

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    He simply abides. SD_GR's Avatar
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    Clean the MAF. Use a product specifically designed for a MAF sensor. Make sure it is cleaned very well, reconnected correctly, and that the air filter is clean and the filter cover is well seated on its tabs.
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    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
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    Supporting Member mjboudreaux77's Avatar
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    Very disspointed...

    Subaru takes a look at the car, and tells me it is the exhaust air flow sensor. I argued stating I wouldn't think that sensor would make the car buck so violently, but they dismissed my thoughts and ordered the part - which means they keep the car overnight (evidently, Subaru dealers don't stock parts on hand).

    I get the call today, and now they tell me that the MAF is ALSO bad - so I will have to wait until Monday to get my car back. While the MAF has a higher chance of being the culprit, I am still not convinced.

    The worst part...... the loaner I got was a Prius.
    If I don't die by Thursday, I'll be roarin Friday night - Jimmy Buffett

  8. #7
    He simply abides. SD_GR's Avatar
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    Quote Originally Posted by mjboudreaux77 View Post
    Very disspointed...
    Just a thought, since I've seen this CEL repeatedly:

    Quote Originally Posted by SD_GR
    Clean the MAF. Use a product specifically designed for a MAF sensor. Make sure it is cleaned very well, reconnected correctly, and that the air filter is clean and the filter cover is well seated on its tabs.
    PO171 is a frustrating CEL since it seems to rarely reflect directly the cause of the issue. With your air filter setup I would not be surprised at all if a MAF cleaning would do the trick. I am not trying to second-guess your dealer -- mainly because I'm not near the car after all -- and what the dealer is planning is in fact likely to fix the problem, but I tend to start cheap and then escalate in costs when troubleshooting. Just IMO.
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

  9. #8
    Supporting Member mjboudreaux77's Avatar
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    Got my car back... Seems like the MAF was the culprit. So far so good, but I have only driven 2 miles since I got it.

    The highway ride home tonight will tell all...

    After driving a Prius for the better part of a week, I am lovin the WRX.
    If I don't die by Thursday, I'll be roarin Friday night - Jimmy Buffett

  10. #9
    Registered User BrandonPaquette's Avatar
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    i was looking for a aftermarket maf can anyone help me for 2002 wrx

  11. #10
    Moderator Donkey's Avatar
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    Stop bumping posts. You have already posted a thread on this. Nobody makes an "aftermarket MAF". If you mean replacement Google would have your answer in like 10 seconds.............
    Resident Adviser @ WTF Tuning, LLC
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  12. #11
    Registered User BrandonPaquette's Avatar
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    ok i have the p0171 and cant find out what to do i when back to stock inatke/ clean maf/ injetor clean/ and looked over vacum hose. i need help i was having a hard time starting the car but fix that with injetor cleaner.now the car starts good and ilde rpm are back at 750 as at 500. so i as hoping that clean would fix everthing but after 60 km and 10 -15 start up the kight came back on. and i change the spark plug E3 (E3.64) but had the code before doing so
    Brandon Paquette

  13. #12
    Registered User BrandonPaquette's Avatar
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    what side is bank 1 on a 2002 wrx. if you are sitting in the driver seat is bank one on the left or right side
    Brandon Paquette

  14. #13
    He simply abides. SD_GR's Avatar
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    Quote Originally Posted by BrandonPaquette View Post
    what side is bank 1 on a 2002 wrx. if you are sitting in the driver seat is bank one on the left or right side
    There is only one bank. Bank 1 in this instance does not refer to a side of the motor.
    WRX Info Links, Courtesy TheJ
    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

  15. #14
    Registered User BrandonPaquette's Avatar
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    i see well thanks
    Brandon Paquette

  16. #15
    Registered User BrandonPaquette's Avatar
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    when you unplug the MAF and the car runs the map system dose the cyctem take information for the front anf rear o2 sensor to help decside how much gas to add?
    Brandon Paquette

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