Materials to Maintain Your ZHP IIIII Hand Protection IIIII Tools to Maintain Your ZHP
Results 1 to 8 of 8
  1. #1
    Join Date
    Dec 2014
    Location
    jacksonville FL
    Posts
    171

    MAF can die without die with no codes / softfail

    writing this in hopes it will help someone else along the way...

    I was very skeptical that a MAF (mass air flow sensor) could fail and still be provide ODBII data that appeared appropriate throughout the RPM range. well, I am skeptical no more.

    I was getting an occasional lean condition code, bank 1 and bank 2 (P0171, P0174). over the course of a few months i changed the upper and lower boots, all vacuum lines, fuel filter, disa valve, cleaned the MAF, smoked the intake, replaced the CCV and hoses with no success... when I check my fuel trim, my Long Term trims were steady at ~ 10-14 throughout the RPM range.

    when I replaced the MAF and put ~40 miles on it, my fuel trims are holding steady at ~ 1, success!!

    so yes, a MAF can definitely soft-fail and appear as though it is working just fine when you observe the live data feed readings on your OBDII scanner. mine was apparently ~10% off throughout the rpm range, very precise, but not accurate (for all you engineers)!!!!!

  2. #2
    Join Date
    Dec 2014
    Location
    jacksonville FL
    Posts
    171
    sorry for abysmal subject... it must be to early...

  3. #3
    Join Date
    Feb 2014
    Location
    Kitchener, ON
    Posts
    6,036
    thanks for the good diagnostic info, regardless of typos.

    peter
    peter

    2004 330i ZHP
    2005 330iT ZHP
    2010 328iT M Sport

  4. #4
    Join Date
    Jan 1970
    Location
    Branford, CT
    Posts
    16,055
    This is what happened to me. Eventually the lean codes stayed, though the car functioned fine.
    BP
    2005 330i ZHP / 6MT
    Imolarot / Naturbraun
    2003 330iT / 6MT
    Orientblau / Naturbraun




    It's not the car you drive, it's how you drive it.

  5. #5
    Join Date
    May 2013
    Location
    Baton Rouge, LA
    Posts
    760
    Did you see a drop in mpg etc? Symptoms other than codes?

  6. #6
    Join Date
    Feb 2014
    Location
    New Jersey
    Posts
    70
    Interesting diagnostic info, and agrees with an article I just read the other day:

    http://www.autoserviceprofessional.c...for-you?Page=2

    Basically, if you add your long term fuel trim number and short term fuel trim together, it should not be more than 10%. The article goes on to say that a faulty MAF will cause positive fuel trim numbers, as the sensor is under reporting the amount of airflow.

  7. #7
    Join Date
    Sep 2011
    Location
    San Francisco, CA
    Posts
    6,847
    This is good to know. I will have to check my car. I've been hunting a lean code for awhile now.

  8. #8
    Join Date
    Dec 2014
    Location
    jacksonville FL
    Posts
    171
    Other than the occasional SES light, not really any symptoms. Yeah, the fact that the LTFT + STFT stayed relatively high, throughout the RPM range is what finally convinced me to pony up and replace the MAF.. since the lean condition didn't get much better at higher RPM, it ruled out further vacuum leaks, which ofcourse is the most likely culprit.

Similar Threads

  1. BMW Option Codes
    By Marcus-SanDiego in forum General -- ZHP Related
    Replies: 85
    Last Post: 01-21-2017, 11:11 AM
  2. Codes, codes everywhere!
    By Asiah119 in forum Mechanical | Troubleshooting
    Replies: 9
    Last Post: 07-14-2013, 10:57 AM
  3. Need some help with codes
    By Asiah119 in forum Mechanical | Troubleshooting
    Replies: 3
    Last Post: 09-14-2012, 04:16 AM
  4. Need a little help deciphering these codes
    By static667 in forum Mechanical | Troubleshooting
    Replies: 5
    Last Post: 07-11-2012, 07:55 PM
  5. SES light on. How can I get the codes?
    By static667 in forum Mechanical | Troubleshooting
    Replies: 6
    Last Post: 09-11-2011, 06:50 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •