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Thread: code 171/174 question

  1. #1
    Join Date
    Apr 2004
    Location
    kissimmee fl
    Posts
    77
    My Cars
    92 325i

    Question code 171/174 question

    hello to all
    is it possible for code po171 bank1&po174 bank2 be a false positive. the light comes on then it goes out by self.
    i bought this car last month and as prevented maintenace i'm changing both rubber boots for TB and valve cover gasket. also o ring in disa valve.
    i've clean the mass sensor with the mass airflow spray. usually the codes are from vacuum leak. but why would the light go out on it's own if it has a vacuum leak.
    the previous owner had all 4 02 sensors change any suggestion or ideas thanks

  2. #2
    Join Date
    Mar 2016
    Location
    Portland, OR
    Posts
    712
    My Cars
    2002 325Ci Cabriolet
    These are the two most common codes that an E46 will throw. It can be a never ending battle for some. Check to see if your DISA passes a vacuum check. Mine failed a vacuum check so I replaced it. I then went more than 1000 miles without seeing either code and then in less than 100 miles after checking the oil, code P0171 is 'pending'. A smoke test is also a good way to find a vacuum leak. I have come to conclude that if there is a very small vacuum leak, it can throw a code while the engine is cold but once the engine warms and vacuum hoses expand, the vacuum leak can seal itself. This is just my theory.

  3. #3
    Join Date
    Apr 2004
    Location
    kissimmee fl
    Posts
    77
    My Cars
    92 325i

    Question

    thanks i've replace the boot that connects to the TB but today i notice when i jack the car up and look up at the intake that the IDLE REGULATING VALVE was sticking out about 1/2 from intake i guess the previous owner must of had it out as i just got this car late feb of this year any way i push it in and now it seems it made the fuel trims worse so to start fresh i order a new
    Rubber grommet thanks for the reply


    Quote Originally Posted by All2kool View Post
    These are the two most common codes that an E46 will throw. It can be a never ending battle for some. Check to see if your DISA passes a vacuum check. Mine failed a vacuum check so I replaced it. I then went more than 1000 miles without seeing either code and then in less than 100 miles after checking the oil, code P0171 is 'pending'. A smoke test is also a good way to find a vacuum leak. I have come to conclude that if there is a very small vacuum leak, it can throw a code while the engine is cold but once the engine warms and vacuum hoses expand, the vacuum leak can seal itself. This is just my theory.

  4. #4
    Join Date
    Nov 2017
    Location
    Netherlands
    Posts
    16
    My Cars
    E46 320i 2001
    I ended up replacing the water separater what was broken off. ( its a commen problem ) ,
    its a bitch of a job to replace if you have big hands like me ( had to pull the intake manifold in the end )
    but solved my idle problem, oil leak ( mostly ) and cleared out the error code's.

    Might want to try if you can follow that plastic tube that runs up from the oil-dipstick.. it might be broken clean-off
    at the start of the "black box thingy" what separates water from the oil.

    Cheap parts.. lots of work.

  5. #5
    Join Date
    Apr 2004
    Location
    kissimmee fl
    Posts
    77
    My Cars
    92 325i
    i already change that drain hose when i change the other stuff with it

    Quote Originally Posted by Stefan666 View Post
    I ended up replacing the water separater what was broken off. ( its a commen problem ) ,
    its a bitch of a job to replace if you have big hands like me ( had to pull the intake manifold in the end )
    but solved my idle problem, oil leak ( mostly ) and cleared out the error code's.

    Might want to try if you can follow that plastic tube that runs up from the oil-dipstick.. it might be broken clean-off
    at the start of the "black box thingy" what separates water from the oil.

    Cheap parts.. lots of work.

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