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    VWVortex


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    Thread: P0171 Fuel Trim,Bank1 System too Lean

    1. 11-30-2007 11:32 PM #1
      okay, this is what has been done so far in an attempt to resolve the DTC Error Code P0171:

      replaced the MAF(Air Mass Meter)

      ran a fuel pressure test inline and got these readings:

      36psi with ignition on but not started
      38-39psi with engine running

      - plugged the fuel return line and the pressure jumped up past 60psi
      which the book recommends replacing the fuel regulator but i already did with a used one unless the second one is also bad.

      - noticed when relieving the fuel pressure by removing the gas cap, no pressure release sound was heard like all the other vehicles ive ever removed the gas cap from. does that indicate a faulty fuel system?

      - don't know if this problem is related, but when turning the ignition switch on there is a high-pitched wheezing noise coming from the Throttle Control Module located on the side of the throttle body.

      see picture:

      already disconnected the battery to reset the ECU, but after the car warmed up the error came back again. any suggestions in getting rid of the DTC P0171 error code?


      other than the error code, the car runs great!





      Modified by icekooled at 8:35 PM 11-30-2007


    2. Senior Member bluefox280's Avatar
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      12-01-2007 12:41 PM #2
      Quote, originally posted by icekooled »
      - don't know if this problem is related, but when turning the ignition switch on there is a high-pitched wheezing noise coming from the Throttle Control Module located on the side of the throttle body

      No that's not related. That high-pitch frequency noise is normal.
      That's the throttle actuator on the throttle body since it's a drive-by-wire vehicle.

      Quote, originally posted by icekooled »
      already disconnected the battery to reset the ECU, but after the car warmed up the error came back again. any suggestions in getting rid of the DTC P0171 error code?

      * VW DTC 16555 (P0171) - Fuel Trim, Bank1 System too Lean

      The ECU is seeing a fuel trim that's much too lean even with the ECU making adjustments.
      That means either the MAF is dead again (can be verified with VAG-COM), or there's a problem with the pre-cat O2 sensor, or there's a significant vacuum leak.
      Should be an easy fix if you have access to a VAG-COM (diagnostic scan tool).
      You need to confirm / deny working parts with a 2nd gear pull data-logging measuring blocks 002, + 032.

      - Erik

      P.S. Pulling battery power from the ECU doesn't clear the codes on OBDII systems.

      Pattern Draft Imaging.com - "...Where Engineering Discipline and Photography Merge as One..."

    3. Member IRL-Euro's Avatar
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      12-01-2007 01:01 PM #3
      check combi valve for a vacuum leak you can see it in your pic below the T/B and the hose from the fuel psi reg to manifold most common problem on the 2.0l

    4. Member I haz cheezeburgerz's Avatar
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      08-08-2009 02:50 PM #4
      Quote, originally posted by bluefox280 »

      * VW DTC 16555 (P0171) - Fuel Trim, Bank1 System too Lean

      The ECU is seeing a fuel trim that's much too lean even with the ECU making adjustments.
      That means either the MAF is dead again (can be verified with VAG-COM), or there's a problem with the pre-cat O2 sensor, or there's a significant vacuum leak.
      Should be an easy fix if you have access to a VAG-COM (diagnostic scan tool).
      You need to confirm / deny working parts with a 2nd gear pull data-logging measuring blocks 002, + 032.

      - Erik

      I'm trying to diagnose the problem on a 01 2.oL automatic...
      I don't know how to use VAG-COM well enough, and I need someone to basically walk me though this...can I get some help fellas?
      Thanks in advance.

      Looking for a mk3 "GTI" front grille emblem, mk3 font (not 20 Jahre "block" font)

    5. Member I haz cheezeburgerz's Avatar
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      08-08-2009 03:30 PM #5
      no-one, eh.
      Looking for a mk3 "GTI" front grille emblem, mk3 font (not 20 Jahre "block" font)

    6. Member CapitalDan's Avatar
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      08-08-2009 03:35 PM #6
      PCV Hoses, Mass airflow, or you could be like me and pull a dixie cup of sand out of your fuel pump
      I'm ridin round Im gettin it, I'm ridin round Im gettin it

    7. Member I haz cheezeburgerz's Avatar
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      08-08-2009 03:39 PM #7
      maybe I quoted too much of blue fox's post the last time

      Quote, originally posted by bluefox280 »
      You need to confirm / deny working parts with a 2nd gear pull data-logging measuring blocks 002, + 032.

      I don't know how to do this.
      02 sensors are new
      no vaccum leaks
      maf was cleaned
      I need to use the VAG-COM to check the parts and I don't know how to do it.

      Looking for a mk3 "GTI" front grille emblem, mk3 font (not 20 Jahre "block" font)

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